Powerline Comparison of Features & Functionality: Expanding your Powerline Adapter Home Network

If your home or small business has a Powerline network, there may come a time when you wish to expand your network. This could be to add wired connectivity in a different room or to a new WiFi access point. Offering better coverage for mobile and fixed wireless devices than your main router can provide.

It is not always clear from the manufacturers site which part number(s) you should buy in order to expand your existing network. Most Powerline units are sold as initial getting started kits only with little information on how to grow your network.

This Powerline Adapter Comparison attempts to simplify the options in making Powerline product choices.

 

Contents

The following seeks to clarify some easily misunderstood and often muddied points about Powerline.

Feature Comparison

The Powerline Comparison is divided into comparing the Powerline Adapter ranges of the six main Powerline manufacturers.

Common Questions

  1. How many adapters do I need?
  2. Can I mix and match different manufacturers adapters?
  3. I can get a 2000 Mbit/s Powerline adapter, seems like a no brainier to make my computer/Internet faster?
  4. When shouldn’t I use Powerline adapters?
  5. What should I tell my electrician if I’m having work done?

Feature Comparison: Expanding Your Network

The following table can be used to help you expand your Powerline network. For each manufacturer they show the combination of WiFi, Ethernet Port Numbers and Passthrough Port availability. Manufacturers are displayed in alphabetical order.

Passthrough: Passthrough means that there is a standard electrical socket on the front of the Powerline adapter, allowing you to plug the Powerline adapter into the wall without sacrificing access to the electrical socket for other devices.

e(#) = 1Gbps Ethernet

e(#) = 100Mbps Ethernet

(#) represents the number of Ethernet ports present on WiFi adapter modules

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Asus

WiFi
1 Port Ethernet
2 Port Ethernet
3 Port Ethernet
4 Port Ethernet
Range Max Speed Mbit/s No
Pass-through
Pass-through No
Pass-through
Pass-through No
Pass-through
Pass-through No
Pass-through
Pass-through No
Pass-through
Pass-through
AV1200 1200 PL-AC56 (802.11ac 867) e(3)
PL-E56P e(1)
AV600 600 PL-E52P e(1)
AV500 500 PL-N12 (802.11n 300) e(2)
PL-E41 e(1)
PL-X51P e(4)
AV200 200 PL-X31M e(1)

BT

BT Powerline adapters are not internationalised and only come with UK 240v plugs.

WiFi
1 Port Ethernet
2 Port Ethernet
3 Port Ethernet
Range Max Speed Mbit/s No
Pass-through
Pass-through No
Pass-through
Pass-through No
Pass-through
Pass-through No
Pass-through
Pass-through
1200 1200 11ac Dual-Band Wi-fi Extender 1200 080462 (802.11ac 867) e(1)
1000 1000 Wi-Fi Home Hotspot 1000 088156 (802.11ac 583) e(1) Broadband Extender 1000 088158 e(1) Broadband Extender Flex 1000 080219 e(2)
1000 600 11ac Wi-Fi Home Hotspot Plus 1000 080461 (802.11ac 867) e(1) Mini Connector 087372 e(2)
750 750 11ac Dual-Band Wi-Fi Extender 750 85854 (802.11ac 733) e(1)
600 600 Dual-Band Wi-fi Extender 610 083530 (802.11n) e(1) Broadband Extender 600 084284 e(1) Broadband Extender Flex 600 084285 e(1)
Wi-Fi Home Hotspot Plus 600 084286 (802.11n) e(2)
Mini Wi-Fi Home Hotspot 600 084288 (802.11n) e(2)
300 300 Essentials Wi-Fi Extender 300 088159 (802.11n)

D-Link

WiFi
1 Port Ethernet
2 Port Ethernet
3 Port Ethernet
Range Max Speed Mbit/s No
Pass-through
Pass-through No
Pass-through
Pass-through No
Pass-through
Pass-through No
Pass-through
Pass-through
AV2000 1900 DHP-701AV e(1)
AV1000 1000 DHP-W610AV (802.11ac 867) e(1) DHP-601AV e(1) DHP-P610AV e(1)
DHP-W611AV (802.11ac 867)
e(1)
DHP-P601AV e(1)
AV500 500 DHP-W310AV (802.11n) e(1) DHP-P509AV e(1)
AV200 200 DHP-309AV e(1)

Devolo

WiFi
1 Port Ethernet
2 Port Ethernet
3 Port Ethernet
Range Max Speed Mbit/s No
Pass-through
Pass-through No
Pass-through
Pass-through No
Pass-through
Pass-through No
Pass-through
Pass-through
dLAN 1200 1200 dLAN 1200+ e(1) dLAN 1200 triple+ e(3)
dLAN 1000 1000 dLAN 1000 duo+ e(2)
dLAN 650 650 dLAN 650+ e(1) dLAN 650 triple+ e(3)
dLAN 550 550 dLAN 550 duo+ e(2)
dLAN 500 500 dLAN 500 duo e(2)

NetGear

WiFi
1 Port Ethernet
2 Port Ethernet
3 Port Ethernet
Range Max Speed Mbit/s No
Pass-through
Pass-through No
Pass-through
Pass-through No
Pass-through
Pass-through No
Pass-through
Pass-through
PL2000 2000 PLP2000 e(2)
PL1200 1200 PL1200 e(1) PLP1200 e(1)
PL1000 1000 PLW1000 e(1) (802.11n 300) PL1000 e(1) PLP1000 e(1)
PLW1000v2 e(1) (802.11n 300)
PLW1010 e(1) (802.11ac)
PLW1010v2 e(1) (802.1ac)
PL500 500 XWN5001 (802.11n 300) e(1) XAVB5101 e(1) XAVB5401 e(1) XAVB5602 e(2)
XAVB5201 e(1)
XWN5021 (802.11n 300) e(1) XAVB5221 e(1) XAVB5421 e(1)
PL200 200 XAVB1301 e(1)

TP-Link

WiFi
1 Port Ethernet
2 Port Ethernet
3 Port Ethernet
Range Max Speed Mbit/s No
Pass-through
Pass-through No
Pass-through
Pass-through No
Pass-through
Pass-through No
Pass-through
Pass-through
AV2000 2000 TL-WPA9610 (802.11ac 1200) e(1) TL-PA9020 e(2) TL-PA9020P e(2)
AV1300 1300 TL-WPA8630P (802.11ac 1350) e(1) TL-PA8010P e(1)
AV1200 1200 TL-WPA8730 (802.11ac 1750) e(3) TL-PA8010 e(1) TL-PA8030P e(3)
TL-WPA8630 (802.11ac 1200) e(3)
AV1000 1000 TL-WPA7510 (802.11ac 433) e(1) TL-PA7010 e(1) TL-PA7010P e(1) TL-PA7020 e(2) TL-PA7020P e(2)
AV600 600 TL-WPA4220 (802.11n 300) e(2) TL-PA4010 e(1) TL-PA4010P e(1) TL-PA4020P e(2)
AV500 500 TL-WPA4530 (802.11ac 433) e(3) TL-PA4010 e(1) TL-PA4020P e(2)

TRENDnet

WiFi
1 Port Ethernet
2 Port Ethernet
3 Port Ethernet
4 Port Ethernet
Range Max Speed Mbit/s No
Pass-through
Pass-through No
Pass-through
Pass-through No
Pass-through
Pass-through No
Pass-through
Pass-through No
Pass-through
Pass-through
1300 AV2 1300 TPL-430AP e(3) (802.11ac 866) TPL-422E e(1) TPL-423E e(1)
1200 AV2 1200 TPL-420E e(1) TPL-421E e(1)
500 AV 500 TPL-410AP e(2) (802.11n 300) TPL-408E e(1) TPL-407E e(1) TPL-405E e(4)
TPL-406E e(1)
TPL-401E e(1) TPL-4052E e(4)
200 AV 200 TPL-331EP e(1)

e(#) = 1Gbps Ethernet

e(#) = 100Mbps Ethernet

(#) represents the number of ethernet ports present on WiFi adapter modules

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Buying Tips & Recommendations

If you are using the Powerline Comparison to create a new or expand an existing network. The following tips may offer some guidance.

  1. If you live in a flat, apartment, communal living (e.g. Student accomodation) ony consider devices with AES encryption.
  2. When expanding your existing network consider now whather you want to start swapping out any older devices. If you do, stick to the same manufacturer, but go to their newer models. If you do not, stick to the same manufacturer and range for the best  interoperability.
  3. Wired Powerline network users should only consider new adapters with 1Gbps ethernet. The adapter should have a minimum Powerline bandwidth of 1000 Mbit/s.
  4. If you intend to create a wired network with more than two wired ethernet device connected, and will be making non-Internet file transfers (e.g. backing up to a NAS or PC to PC file copy). Only look at the 2000 Mbit/s Powerline ranges.
  5. When creating a new wireless Powerline network. Only look at the 802.11ac ranges.
  6. If your broadband Internet connection is fast (e.g. true fibre optic) ideally do not let any single part of the Powerline network be slower than your broadband connection.

 

Common Questions

How many adapters do I need?

It is not always clear to new users starting out with Powerline adapters that you can expand the network beyond the first two appliances that you will probably have (or will) purchased in a starter kit bundle.

Powerline is in essence a broadcast technology, meaning that it is not limited just to the first two devices that you place in your home. Neither is is necessary to operate any subsequent device that you add in a pair of devices – so you do not have to have 4,6,8 adapters live at any one time and can just as easily have 3, 5 or 7 adapters live on your network.

You do have to have more than 1 adapter however!

 

Can I mix and match different manufacturers adapters?

‘Powerline’ is a technical standard, not a proprietary solution to each manufacturer – although they may add proprietary innovations on top of the standard. This means that in practice you should be able to mix and match Powerline devices from different manufacturers on your network provided that the product is advertising standards compliance to the following certification combinations.

Standard Max Line
Speed (standard)
Max Client
Speed (standard)
Backwards Compatibility Notes
IEEE 1901 500 Mbit/s
IEEE 1905.1 / nVoy HomePlug n/a The standard for Powerline + Wifi devices
HomePlug 1.0 14 Mbit/s IEEE 1901
HomePlug 1.0 turbo 85 Mbit/s IEEE 1901
HomePlug AV 200 Mbit/s 80 Mbit/s IEEE 1901, HomePlug 1.0 (in theory) ‘AV’ standard for Audio/Video
HomePlug AV2 1000 Mbit/s IEEE 1901, HomePlug AV, HomePlug 1.0 (in theory)

Being standards compliant does not mean that an individual manufacturer or model of Powerline adapter will actually meet the performance levels prescribed by the standard. It also does not prevent the adapter from exceeding the standard either under conditions defined by the manufacturer.

The standard exists to ensure that if you mix your ecosystem, you can expect that under optimal conditions, the devices will operate at the speed advocated for by the standard – but not (necessarily) at the maximum capable speed of both/either device. Conversely, if you do not mix your ecosystem, and only use devices made by manufacturer x, your realised real-world performance may instead be higher than that advocated for by the standard. Consequently, it is generally recommended that where possible you stick to the same manufacturer for your Powerline network and ideally the same series/range of device.

 

I can get a 2000 Mbit/s Powerline adapter, seems like a no brainier to make my computer/Internet faster?

Having looked at many reviews and videos on the subject, this topic is horribly misunderstood by people ‘in the know’ to the extent that they are further confusing the issue with false information. There are 5 aspects that influence why a typical single computer/single WiFi Extender scenario isn’t in most cases going to mean a 2000 Mbit/s solution will deliver.

Electrical wiring, distribution, electrical noise and distance: The age and quality of your home electrical system will have an impact on the performance. If your electrical system isn’t up to 2000 Mbit/s, you will never see anything like that speed, possibly pulling the performance down under 100 Mbit/s. Equally, the longer the distance between the adapter termination points, the more this figure will trail off.

IEEE 802.3 (ethernet): If you are going to connect your desktop PC at one end to your router at the other (and you have modern equipment) then the Ethernet cable and the network adapters at your computer/router are only capable of a theoretical maximum of 1000 Mbit/s. Having a 2000 Mbit/s Powerline adapter will not make this point-to-point, two device network any faster even if the Powerline adapter does operate at a speed higher than 1000 Mbit/s.

IEEE 802.11 (wireless): Similarly to that of the Ethernet, wireless technology is also rated at a maximum theoretical speed 54 Mbit/s for 802.11a/g, 11 Mbit/s for 802.11b, 600Mbit/s for 802.11n and up to 3466 Mbit/s for 802.11ac – in practice it usually isn’t more than ~ 1300 Mbit/s on current generation general consumer hardware. If the WiFi Access Point module on the Powerline adapter is only capable or 600 Mbit/s or your laptop/tablet/smartphone are only capable of 600 Mbit/s, having a faster Powerline adapter will not make your wireless any faster.

Internet Connection Speed: Most home installs are probably just being used to push the Internet connection arriving at your router a little further into your property, usually because you need it to reach into another room that is out of range of the existing wireless access point. Most home internet connections (in the UK) at the current time run at sub-100 Mbit/s. Assuming that your Powerline adapter is 2000 Mbit/s, your wired desktop is 1000 Mbit/s and your tablet is 600 Mbit/s, you will not get anything faster from the Internet than the 100 Mbit/s maximum speed of your home broadband. A faster Powerline adapter can not improve the spped of your actual Internet connection to the street.

Contention: This is the most important one that people misunderstand. Powerline is what is known as a contended broadcast medium. This means that every piece of information sent to one Powerline adapter is received and processed by all of the other Powerline adapters on the network. If you have 4 Powerline adapters that try and access the network simultaneously, then the available maximum bandwidth (e.g. 2000 Mbit/s) must be shared between them. There are more sophisticated underlying technologies in newer Powerline adapters, such as OFDM and latterly MIMO that significantly help to improve this, however the key thing to understand is that the 2000 Mbit/s figure on the box is the speed available to the holistic group of all Powerline adapters on the network and must be shared amongst all termination points.

In the case of OFDM bandwidth is shared as a proportion of the total frequency spectrum available to each adapter while in the case of MIMO it is shared up to the number of available MIMO channels. For very old adapters, the full bandwidth was available, but only one Powerline adapter could communicate on the network at any one time; during which time the other adapters had to wait.

At the beginning of this section I stated that getting faster network performance it isn’t a reality in most cases. So where is it a benefit?

The benefit of having the faster line speed (the maximum theoretical bandwidth available to the group of Powerline adapters) is when there are multiple end-point devices and/or multiple Powerline adapters.

Take a scenario where Internet access is removed from the equation and pretend that there are 4 Powerline adapters, A, B, C and D. Each Powerline adapter has a single wired ethernet connection running at 1Gb/s (1000 Mbit/s). If computer A copies a file to computer B while computer C copies a file to computer D and you have 2000 Mbit/s available to the Powerline network, simplified, a 1000 Mbit/s file copy + another 1000 Mbit/s file copy (with access to MIMO) = 2000 Mbit/s. So the 2000 Mbit/s adapter will in theory allow both copies to occur at the 1Gb/s line speed (full speed).

Again, this is a theoretical figure and there are a lot of variables that will define the actual speed. In reality you may only get 800 Mbit/s during the parallel transfer (1600 Mbit/s total), but this is only achievable because the Powerline back-end is capable of supporting the higher line speed. If the Powerline network was only itself capable of 1000 Mbit/s, then the best you could have hoped for during this parallel file transfer would have been 500 Mbit/s. This is the impact of contention.

In practice, there are a lot of tweaks and optimisation’s to how OFDM, MIMO and proprietary manufacturer innovations are applied on different products. These tweaks make the examples that I have outlines significant simplifications over what may actually be going on in any given Powerline adapter. It is also true that the Powerline network will likely not run anywhere near its theoretical maximum speed, bringing down the contended bandwidth figure that you are starting out with.

In these cases a faster device with MIMO and more frequency groups available may help you to realise slightly faster speeds. It is however important to understand what the figure on the box is actually telling you -and- to set expectations (and even save money) with end users.

Simply put: If you are only looking to have a point to point link and are only ever going to be using it to access the Internet there is usually little point spending money on faster Powerline modules for your use case.

 

When shouldn’t I use Powerline adapters?

Powerline should not be used if:

  1. You are involved in any form of secure network or secure data workflow. Powerline can easily leak data to your neighbours or into the street. Modern adapters usually come with AES 128 encryption support as an option, however AES 128 is not the strongest form of encryption by any means here in 2018. Equally, firmware updates and patches for Powerline adapters to fix security holes are not applied automatically. Unfortunately, neither are they made available by some manufacturers as frequently as they should be.
  2. If AES Encryption technology is illegal in your country: do not use an AES enabled device.
  3. You do not have direct access to a wall socket: Powerline adapters should not be used on power gangs, PDU’s or through surge protectors. If you do, at best they will either have significant signal degradation or will not work.
  4. If the length of your internal wiring is over 300m (try and keep it far shorter than this in practice i.e. under 200m).
  5. Your house has extremely old wiring or archaic distribution / fuse boards.
  6. You want to get a good signal across multiple distribution boards / fuse boards.
  7. The electrical system has a high number of noisy appliances and you are expecting to get performance out of the system.

 

What should I tell my electrician if I’m having work done?

If you are having work done or want to get an electrician in to troubleshoot poor Powerline adapter performance. Offer them the following tips and get ready with a laptop, ethernet cable and a test plan (e.g. SpeedTest.net, benchmark tool or a consistent large file copy).

  1. The electrician needs to provide a low-loss RF path across all circuits, and rings. The system requires low levels of electrical noise.
  2. Aluminium wiring, knob and tube wiring, old copper wiring, old fuse boards, distribution boards and sockets will undermine the performance. Unless it is 1990’s or newer, try and eliminate it from the system.
  3. Arc-Fault Circuit Interrupter (AFCI), Arc-Fault Detection Device (AFDD), Ground Fault Circuit Interrupter (GFCI), or Residual Current Device (RCD) circuit breakers can cause depleted or even entirely blocked Powerline signals. You can purchase “Powerline Compliant Outlet” surge protectors, which may mitigate some of the loss.
  4. Devices with switch-mode power supplies can create noise that limits performance. Isolate such devices before testing (especially near the receiver Powerline unit).
  5. Any appliance on your power system/ring with an electrical motor should be placed on its own surge protector e.g. air-conditioners, washing-machines and electric-fans.
  6. Remember the distance rule: Under 300m, ideally under 200m. This is especially important in the UK where rings are used allowing a run to be far longer than it might otherwise seem.
  7. 3-phase electrical systems do not work as well with Powerline. Avoid their use if possible in favour of 2-phase.
  8. If you are in a communal building, or high density residential environment, use a circuit breaker from the street to reduce the risk of data leakage out of your home.
  9. Loose screws, poor joints and thin or frayed cabling at connections can all cause problems. Ensure that everything is nice and tight.
  10. Crossing between ring mains will attenuate performance. Where possible keep adapters on the same ring main.

Netgear ReadyNAS Duo v2 as a Windows Server Backup Target across SMB while allowing differencing in the backup type

System Requirements:

  • Netgear ReadyNAS Duo v2 or any SMB capable NAS
  • Windows Server 2008, 2008 R2, 2012, 2012 R2

The Problem:

One of the most frustrating “features” of Windows Server since the release of Windows Server 2008 has been the backup set. Windows Server Backup added support for backing up to SMB, however only if you perform a full, rather than incremental or differential backup of the host server.

The main problem with this is the time it takes to perform the backup. Depending on the size of the disk array involved, a normal backup job can take tens of hours, even days. If you want to run the backup job daily and the job is taking more than a day to complete while saturating the network, then it is not a very effective backup solution.

Yet the real power in using the network in the first place is the fact that it permits the distribution of the backup to a remote location without the need to go and physically disconnect a drive and carry it. The drives can also be a lot further away than with USB, eSATA or firewire. In another building or in another country.

Further more, the array is more expandable than a typical USB disk. The maximum supported size of this little ReadyNAS duo v2 is 2x4TB in RAID 0, resulting in 8GB of storage. I could also run it in RAID 1 if I needed higher levels of data security. This is much better than a typical USB disk. With a 4 or 8 bay NAS, you can even grow the array by adding new drives and expand the VHDX file according to you needs (up to the limit of the native NAS file system or the NTFS volume limit). Devices with more bays also allow for additional RAID types and associated data security such as RAID 5, 6 or 10.

In many situations, you can use iSCSI for this purpose. Most high end and Enterprise NAS storage and SAN solutions are designed to provide thick or thin provisioned iSCSI targets which you can easily mount via the iSCSI initiator in Windows. An iSCSI mounted drive in Windows is – at least as far as Window is concerned – presented as a local disk and therefore you can perform a differencing backup under the control of Windows Server Backup (WSB).

So what can you do if you have a consumer grade NAS appliance or an old model device that does not expose iSCSI services? A device such as the Netgear ReadyNAS Duo v2? While the v2 version has an unofficial iSCSI Target plugin, this does not work on the v2 model and so having a very low power, ARM based NAS lying around with 6TB of disks in it, it seems a shame to relegate it to the dustbin.

More Info

Storage virtualisation is the answer.

Simply put, Windows Server Backup (WSB) cannot itself perform differential backups to a SMB share, however a SMB share (even a SMB 2.0 share) can host a virtualised storage disk… and Windows can mount a virtualised disk across SMB. Once mounted, WSB is agnostic to the underlying disk location or the fact that it is stored on a SMB share as Windows presents the disk as being locally attached and abstracts the ‘what’ and ‘were’ entirely to the virtualisation layer.

The Test

If you are going to attempt this, I strongly recommend that you enable Jumbo Frames on the device as you may be able to squeeze a 10-20 Mbps of additional write speed out of the device.

View: Netgear ReadyNAS Duo V2 and Jumbo Frames

  1. Ensure that your machine can connect to the ReadyNAS over SMB i.e. \\<ipAddress\<shareName>
  2. Create a share on the NAS for the backup. Create a dedicated one so that you minimise SMB file system update requests to the share. As will be mentioned below, this causes between a 10-20Mbps loss of performance even if nothing is actually happening in Windows Explorer.
  3. Disable as many services as you can on the NAS. The less work the CPU is doing and the more free RAM, the better this will be.
  4. Open PowerShell on Windows 8, 8.1, 10, 2012, 2012 R2 or 2016 and enter:
    New-VHD –Path “\\<ipAddress\<shareName>\Backup.vhdx” –SizeBytes 4096GB

    Substitute the 4096GB (4TB) with the size that you require. This will create a dynamically expanding Hyper-V Virtual Hard Drive on the ReadyNAS

  5. In PowerShell issue the following command to mount the VHDX file
    Mount-VHD -Path "\\<ipAddress\<shareName>\Backup.vhdx"

    Now use DiskPart or Disk Manager to initialise, partition and format the disk. Remember to format it using 64K sectors as this will be important to preserve performance for the large files involved.

    Alternately you can execute the entire initialisation and mounting process in PowerShell using:

    Mount-VHD -Path "\\<ipAddress\<shareName>\Backup.vhdx" -Passthru |Initialize-Disk -Passthru |New-Partition -DriveLetter B -UseMaximumSize
    Format-Volume -DriveLetter B -FileSystem NTFS -NewFileSystemLabel "Backup Disk" -AllocationUnitSize 65536 -Confirm:$false -Force

    This will create a 64K NTFS partition called “Backup Disk” and mount it on B:\ using the VHDX file found on the ReadyNAS

  6. Now, if you attempt to use Windows Server Backup you will be able to create a differencing disk backup set.

Does it work?

Windows Server Backup (WSB) certainly accepts the disk without any complaints and is dutifully able to create the first Normal copy after which it is able to easily perform the delta-backup as would be familiar for an incremental or differential backup type. So yes, it does work. It tricks Windows into accepting the SMB target.

Performance is however a sticking point.

To apply some context: According to a “Legit Reviews” review of the WD Red 5400rpm 3TB drives in the NAS, each drive should easily have been able to manage a write speed of 80MB/s or 640Mbps at a minimum – with something around 147MB/s or 1176Mbps being expected for sequential writes.

Source: WD Red 3TB NAS Hard Drive Review (Page 3)

 

Creating a Hyper-V VHDX file and writing linear zero’s to it across the network results in a write speed variance of between 445Mbps and 495Mbps on the wire (55.6MB/s – 61.25MB/s). The highest that I saw it peak at was 537Mbps in burst.

Performing a backup onto the drive took 23 hours and 2 minutes with the MTU set to 1500 bytes with the average bit rate being approximately 420Mbps – 430Mbps for the backup. Particularly painful for the first normal backup. This is however comparable to the performance of a USB 2.0 drive.

So we can safely conclude that the bottleneck is not the drives. The bottleneck is the ReadyNAS Duo v2. Other, newer devices with more CPU horsepower, more RAM, larger NIC buffers, native Jumbo Frame offload support and more NICs (as well as more drives) should be able to offer better performance.

As an interesting side observation, having a Windows Explorer session sitting open to a SMB share and doing nothing slowed the zeroing process by 10-20Mbps on its own. This highlights the impact of having the NAS CPU performing other actions and its impact of write performance.

Reality Check

There are however some problems here. Windows Server Backup is not aware that this is a virtual drive, it expects the drive to perform and present like a physical hard drive and it will treat it as such consequently

  1. It is going to have poor support for and tolerance of power management (suspend and standby).
  2. It is going to have little to no tolerance for an unreliable network connection i.e. never try to do this over wireless or an unstable Internet connection.
  3. It is going to be extremely susceptible to power outages. You really should use UPS on the NAS, switch(s) and the source machine to prevent data corruption during a power outage. Note that the important part here is that the source machine stops the backup and dismounts the VHDX in the time it spends on the UPS. After that it can all turn off quite happily.
  4. Windows is not going to automatically mount the VHDX. WSB will not do this for you. You will have to either ensure that it mounts as boot or schedule it to mount before the backup.
  5. Windows is going to need to ensure that it cleanly dismounts the VHDX during shutdown and power management operations. WSB is not going to do this for you either.
  6. Use write caching on the NAS and on the host operating system at your risk i.e. definitely have a UPS if you want this performance benefit.
  7. If you need to perform a bare metal recovery of the server, the extra steps of getting the VHDX mounted in the boot recovery environment may prove frustrating.
  8. While VHDX in Server 2012 R2 can technically be ued as a shared medium, you should probably avoid even contemplating trying to share one VHDX between multiple WSB hosts. Create one VHDX for each server.
  9. The current maximum size of a VHDX is 64TB. If this is an issue 1) why are you using a consumer grade NAS? 2) you need a SAN 3) you shouldn’t be using WSB

It should be noted that all of the above postential disadvantages also apply to some degree to the use of iSCSI. The advantage of this approach is that you get the data virtualisation advantage where as with iSCSI your NAS would have to expose this i.e. you can literally just pickup the VHDX and move it to a new HDD, Array, NAS or SAN and WSB isn’t going to care or even notice.

So what can you do? My suggestion is this: do not use the WSB UI to schedule the backup. Use task scheduler and the WSB command line tool WBAdmin.exe to perform the backup in a PowerShell script. Something like the following:

Mount-VHD -Path "\\192.168.0.100\Backup\Backup.vhdx"

Start-Sleep -s 60       # Wait 60 seconds for the disk to come online

C:\Windows\System32\wbadmin.exe start backup -backupTarget:B: -allCritical -include:C: -systemState -vssFull -quiet

Start-Sleep -s 120      # Wait 120 seconds for the disk to go offline

DisMount-VHD -Path "\\192.168.0.100\Backup\Backup.vhdx"

When task scheduler fires the script it will mount the VHDX, wait 60 seconds to allow the file system to mount, perform the backup, wait 120 seconds for the backup sub-system to shutdown and then cleanly dismount the VHDX.

Optimisation and issues

The 256MB RAM, ARM based ReadyNAS Duo v2 was never intended for these kinds of workloads and that does show. Most of the issues encountered with it are simply as a result of the low power, low resource hardware specification.

I have already covered the need to:

  • Use Jumbo Frames on the NIC
  • Do not use wireless connections to mount the VHDX
  • Use 64K sectors on the NTFS volume
  • Optionally use the write cache setting on the ReadyNAS
  • Optionally enable write caching and prevent buffer flushing on the volume as exposed via host operating system

To this I will add the following:

Do not use VHD files, only use VHDX. VHDX are far,far safer to use over SMB compared to VHD as they have error correction and handling built-in. consequently, there is a reasonable chance that the file will actually survive a disconnect of the network cable or power of the source or destination as a result. This does however restrict you to using Windows 8/Server 2012 or higher at the expense of Windows Server 2008/2008 R2

Only use 1Gbps or 10Gbps networks. Do not use 802.11 wireless and do not use 10/100 Fast Ethernet.

Use server grade NICs in your devices if you can

Use MPIO and multiple switches if you can spare/afford the hardware

Keep your VHDX defragged just like any other NTFS formatted hard drive

If you have managed switches, consider preventing broadcast and multicast traffic from reaching the NAS. This will reduce CPU load a little although it will prevent NetBIOS discovery and may impact other services.

Do not use the NAS for anything else, especially small SMB file storage. Client access will degrade the write performance and consume CPU time. In particular do not leave the NAS SMB mount point mounted as a network drive as this also holds a SMB session open with the Linux Samba service.

Do not use dynamically expanding VHDX files. Using a dynamically expanding VHDX file was in reality fine (if you accept the limitations of the device). It took nearly 4TB of data without incident, however the use of dynamically expanding disks is itself inefficient. Dynamic disks have a performance penalty associated with them as the disk head is constantly being told to zero the trailing 12MB of the VHDX file to permit future growth of the VHDX. There are also associated writes to the metadata of the VHDX to update the file boundary markers. In trying to squeeze every last bit of performance out of the ReadyNAS Duo v2, I wanted to use a fixed size VHDX file to see if it was any more performance efficient.

One of the first issues encountered was on the length of time it takes to allocate and deallocate space from the Linux disk journal. Allocation is proportionately faster then deallocation, however on attempting to allocate 5.4TB of disk space to a singe VHDX file, it would take the system an extended period to process and the VHDX creation process on Windows would timeout, causing the VHDX to be corrupted. At this point the VHDX would be deleted by Windows. This storage deallocation could take upwards of 20 minutes to appear as released in the ReadyNAS web UI.

Looking at ‘top’ in the SSH session, it was clear that the CPU was the culprit, capping out at 100% throughout the entire operation before dropping down to <1% once the journal had been updated.

After some trial and error, I found that with the web UI closed, only necessary services running, SSH logged out and no active Windows Explorer sessions open, I could allocate 2TB at a time without it causing a timeout.

The following script can thus be used to create the VHDX at 2TB, expand it to 4TB and then expand it to the desired 5.3TB (the maximum size of the ReadyNAS volume I was using was 5.4TB).

New-VHD -Path "\\192.168.0.100\Backup\Backup.vhdx" –Fixed –SizeBytes 2TB
Resize-VHD –Path "\\192.168.0.100\Backup\Backup.vhdx" –SizeBytes 4TB
Resize-VHD –Path "\\192.168.0.100\Backup\Backup.vhdx" –SizeBytes 5.3TB

Remember, this script is creating a Fixed Size VHDX file. Consequently it is going to pre-zero each sector on the disk instead of performing a constant 12MB zeroing chase at the end of the file. This means that it will take an extremely long time to complete (especially at only ~470Mbps) i.e. over 24 hours! So I suggest that you copy and paste all three lines at once into the PowerShell buffer and walk away. Once it has finished chewing over all three lines, mount the disk, partition it and format it as outlined earlier in the article.

Note: There are a coupe of utilities out on the Internet that can create a fixed size VHDX from free space without performing the zeroing operation. You can save yourself a lot of time using such tools however you should NEVER use them in a production or in a shared environment due to reasons of data safety, privacy and security.

After the allocation of the space in the Journal and during the zeroing process the CPU use remains high, running constantly at 100% with about 20MB of RAM showing as free out of the 256MB total. This proves that the sub 500Mbps cap on the transfer speed is being caused by the CPU and not the disks. You must thus be realistic about the capability of the appliance or pay for more robust, more capable hardware.

You can technically also disable journalling on the volume using SSH, however you must ensure that you have a UPS wired into the NAS and the UPS can perform a controlled shutdown of the NAS if you try and use it. I elected not to do this.

tune4fs -O ^has_journal /dev/sda0
e4fsck –f /dev/sda0
sudo reboot

Final Results

If you have read this and the Jumbo Frames article on the ReadyNAS Duo v2, I am sure that you might be interested to hear what the cumulative impact of all of the performance tweaks and optimisation’s was.

With write caching enabled on both the NAS and the Windows Server and buffer flushing disabled on Windows Server, plus all of the other tweaks listed, backup throughput rose to a fairly consistent 560Mbps – 590Mbps with bursts up to 638Mbps. That equates to 70MB/s – 73.75MB/s and 79.75MB/s at burst. While nowhere near the capability of the drives themselves, it is at least now tantalisingly close to the benchmark value for the drives random write performance test and network write performance is nearly 200Mbps faster.

Performing the backup job (which without any optimisation’s on a Dynamic VHDX took 23 hours and 2 minutes) with all optimisation’s enabled – and actually a significantly larger workload due to the addition of VM state backups in the job – took some 16 and 47 minutes. A considerable improvement! That works out at around 200GB per hour.

Most importantly, when the job ran again the next evening, it took less than 30 minutes thanks to it only having to backup file differences.

So why is this? It is predominantly related to the fixed size VHDX file. The higher throughput is being achieved because the ReadyNAS CPU is sitting at around 5% – 30% idle during the ~600Mbps copy. The Linux file system sees the write process as constituting changes that are internal to the VHDX file and the file itself isn’t growing, therefore the file system driver on the NAS has significantly less work to do. It is instead NTFS on the backup server that is processing the MFT updates into the file allocation table of the VHDX completely transparently to the NAS. This means that the CPU work has been transferred to the backup server, resulting in a performance increase (and a slightly cooler, less power consuming NAS).

Netgear ReadyNAS Duo V2 and Jumbo Frames

System Requirements:

  • Netgear ReadyNAS Duo V2
  • Firmware 5.3.12
  • 9k compatible NIC’s and intermediate Layer 2/Layer 3 hardware

The Problem:

The ReadyNAS Duo V2 is a now legacy, ARM based dual 3.5″ drive SOHO NAS appliance with a single NIC and 256MB of RAM. The device was never intended to support performance or even low-end enterprise tasks.

The ReadyNAS Duo V2 is not designed for Jumbo Frames and there are no user interface entry points to enable it. It is not clear on-line whether anyone has had any actual success with enabling it. This document explores the issue.

More Info

In wanting to use the device simply as a on-line backup appliance, I wanted to try and squeeze as much performance out of it as I could. One of the obvious things to try is to enable Jumbo Frames, which allows more data to be transmitted in a single Ethernet Frame before the data has to be re-wrapped in a new header and trailer for Layer 2 transmission over an Ethernet Network. The logic being that the fewer CPU cycles being used to process the header and generate and process the CRC and footer, the faster the transfer into memory and thus the smoother the transmission of the data can occur into the disk sub-system.

In order the enable Jumbo Frames, the Maximum Transmission Unit (MTU) has to be adjusted on ALL devices in the transmission path – sender NIC, receiver NIC and any and all intermediary switch ports, bridge ports and router ports. If any one devices does not have Jumbo Frames configured to the same (or higher) value, it will fault. If you have one devices with a higher value and the other devices with a lower value, you will almost certainly see a performance reduction when transmitting from that device. Therefore: Set all of your devices to the same, common MTU values.

Depending on the manufacturer, device and driver these are usually:

Name Rounded Offset
Normal
1500
1514
3K
3000
3014
4K
4000
4088
5K
5000
5014
7K
7000
7014
Note: As a general rule of thumb, if you are using a PCI NIC, this is the largest MTU you can hope to achieve. PCI Express NIC’s can go up to 9k
9K
9000
9014
Note: Specialist enterprise grade hardware is required for MTUs larger than 9K and these sizes are not usually available on 1Gbps NIC hardware (10 or 40Gbps hardware or higher)
16K
16000
16128
24K
24000
32K
32000
64K
64000
Note: This is the maximum transfer size of a TCP Segment

Step 1

This was only tested on Firmware Version 5.3.12. Ensure that your firmware is up to date.

Step 2

You will need to enable Root SSH Access on the device via the official Netgear plugin. Install the plugin via the web UI and reboot the NAS before attempting to proceed.

Download: Enable Root SSH Access Plugin

Step 3

Set a static IP address on the device (or at the very least set and then unset it) to ensure that the config files have been written out correctly. It appears that a clean OS install does not make use of the interfaces file as expected until after a static IP address has been set.

Step 4

SSH into the device (using Bash, Putty for Windows or your preferred client). Usually this is root@<ipaddress>

Step 5

Perform a test to see whether Jumbo Frames currently works

ping <ipaddress> -l 8000

If you receive a successful “reply from…” then it is already working between your ReadyNAS and your PC. The expected result is however for this to fail, indicating that Jumbo Frames is not enabled

Step 6

Perform a volatile test by enabling Jumbo Frames for the session. If you lose contact with your single NIC ReadyNAS, simply reboot it to restore functionality. Under the SSH session issue the following command. If you need to set a lower Jumbo Frame value (for example 7k) change the 9000 value as appropriate.

ip link set dev eth0 mtu 9000

Step 7

Repeat the ping test from your PC

ping <ipaddress> -l 8000

This should now be successful

Step 8

If you wish to make the change permanent so that the setting persists after a restart of the ReadyNAS you must edit the interfaces file. Return to the SSH session

vi /etc/network/interfaces

In VI press i to commence insert mode

Find the entry for the eth0 interface and at the bottom of the section enter mtu 9000 (or the frame setting that you require) e.g.

iface eth0 inet static
address 192.168.0.100
netmask 255.255.255.0
gateway 192.168.0.254
mtu 9000

Note: That is LOWER CASE “mtu”

To save and exit VI press the Escape key and then type :wq (colon, w, q) and press return

Finally type reboot to restart the ReadyNAS

Step 9

Repeat the ping test and you should find Jumbo Frames working

Everything went wrong and now I cannot access my ReadyNAS

Don’t panic. Just access the boot menu and put it into OS Reinstall mode

  1. Turn the ReadyNAS off
  2. Use a paper clip to hold in the reset button on the back
  3. Keep the clip held in place and turn the ReadyNAS on
  4. Hold the paper clip in for 10 seconds
  5. Release the paperclip
  6. Push the backup bottom on the front of the ReadyNAS until the Disk 2 LED is the only one illuminated (be very careful that it is Disk 2 and not Disk 1. Disk 2 reinstalls the OS, Disk 1 factory resets the device and deletes all of your data)
  7. Use the paperclip one more time and single press the reset button to execute the boot menu mode
  8. Come back in 20 minutes and use RAIDar to find your ReadyNAS again (you will have to reconfigure the settings)

Does is make a difference?

Comparing the transfer speed before and afterwards does yield a significant improvement in write speed on the device.

The test configuration

The Source

  • 3.4GB ISO
  • Windows Server 2012 R2
  • From an NTFS formatted 5 disk RAID 5 array on a LSI MegaRaid 8260-8i with caching an optimisation’s enabled
  • A Quad Port Intel I350-T4 Gigabit Server NIC with Jumbo Frames set to 9014 bytes
  • Cat 5e cabling
  • 3 intermediate switches all supporting Jumbo Frames

The Destination

  • ReadyNAS firmware 5.3.12
  • Dual WD Red 3TB WD30EFRX-68AX9N0 with 64MB cache (only 5400 RPM)
  • Write caching enabled on the ReadyNAS
  • The ReadyNAS is running in Flex-RAID RAID 0

To enable write caching over SSH:

hdparm -W1 /dev/sda
hdparm -W1 /dev/sda1
hdparm -W1 /dev/sda2
hdparm -W1 /dev/sda3

Transferring the same 3.4GB ISO from the same Windows Server 2012 R2 NTFS volume over the same NIC/Network/Switches with the MTU set at the default 1500 resulted in a non-burst transfer speed of around 43MB/s (344Mbps).

Repeating the transfer with Jumbo Frames set to 9000 enabled increased this noticeably 53MB/s (424Mbps); a 18.86% increase in write speed.

Given that 53MB/s isn’t that stellar in the first place, this improvement is certainly worth having.

Using the NetGear PS101 Mini Print Server without using NetGear Software utilities

System Requirements:

  • NetGear PS101
  • Windows 2000, XP, 2003

The Problem:

NetGear’s hardware can be small and functional, however as with (in my experience) most hardware companies, they cannot write software to save their life – and in a lot of cases when the OS has the capabilities built in, why on earth do these companies feel the need to duplicate functionality, making their hardware difficult to port up to the next version of Windows, once their application ceases working? Let us face it, it just extends their support burden and forces consumers to upgrade to a new product… oh…

The Fix:

When all is said and done, irrespective of what NetGear say, there are Print server standards, and going off to write your own protocol would just be silly. All their PS101 interface application does is provide an incredibly un intuitive, rather messy system to install printer drivers against the Print Server.

You can configure the device just as easily in a manual mode, and chances are you’ll be able to follow this principles of this guide under Linux, Unix, Windows Vista, Windows NT 7, NT 8, NT 9… well, you get the idea.

What you need to know:

Unlike the NetGear application, Windows wont go and probe your network for the PS101, you have to get hold of it yourself and configure it yourself. To do that you need a couple of pieces of information.

  • The IP address of your PS101 – Ask your router, network admin etc)
  • The Device Name of your PS101 – This is on a sticker on the base plate of the PS101, beneath the Serial Number and above the MAC address, or,once you know the IP address by accessing the web configuration in your web browser http://ip.add.re.ss/.
    Note: If you have manually changed the device name, you will NEED to get it from the web configuration program

Before you head off to begin installing your Print Server, I recommend that you ensure your device is running the latest firmware version, these can be obtained from the NetGear support site.

Once you have those two pieces of information and the correct firmware, you are ready to install the PS101. The following steps are written around Windows XP, the process and procedures are similar, if not the same under Windows 2000 and 2003. Other OS’s and Windows versions may vary. Please be aware that you cannot do this under Windows 9x without third party utilities.

  1. Open Printers and Faxes
  2. Double click Add Printer
  3. Select Local Printer and deselect the Automatically detect and install my Plug and Play printer. Click Next
  4. Highlight Create new Port and from the drop box select Standard TCP/IP Port
  5. Click Next to begin the Port wizard
  6. In the Printer Name or IP Address field type the full IP address of your Printer
    e.g. 192.168.0.200
  7. In the Port Name box type the device name of your PS101 suffixed by _P1
    For example, if your device name is PS380460, your Port Name would be PS380460_P1
  8. Click Next, highlight the Custom radio button and click Settings…
  9. The protocol should be set to RAW and the port to 9100. SNMP should remain disabled. Click OK and finish the wizard
  10. After a slight processing pause, Windows will display the Printer driver selection screen. From this point on, simply install your printer as normal.