Unraid in production, a bit rough around the edges, and terrible SMB performance

In my last two posts I described how I migrated from W2K16 and hardware RAID6 to Unraid. Now that I’ve had two Unraid servers in production for a while, I’ll describe some of the good and not so good I experienced.

Running Docker on Unraid is magnitudes easier compared to getting Docker to work on Windows. Docker allowed me to move all but one of my workloads from VM’s to containers, simplifying updates, reducing the memory footprint, and improving performance.

For my IP security camera NVR software I did switch from Milestone XProtect Express running on a W2K16 VM, to DW Spectrum running on an Ubuntu Server VM. DW Spectrum is the US brand name for the Nx Witness product, and the DW Spectrum branded product is sold in the US. I chose to switch to Nx Witness, no DW Spectrum, from XProtect because Nx Witness is lighter in resource consumption, easier to deploy, easier to update, has perpetual licenses, includes native remote viewing, and an official Docker release is forthcoming.

I have been a long time user of CrashPlan, and I switched to CrashPlan Pro when they stopped offering a consumer product. I tested CrashPlan Pro and Duplicati containers on Unraid, with Duplicati backing up to Backblaze B2. Duplicati is the clear winner, backups were very fast, and completed in about 3 days. Where after 5 days I stopped CrashPlan, when it estimated another 18 days to complete the same backup operation, and it showed the familiar out of memory error. My B2 storage cost will be a few $ higher compared to a single seat license for CrashPlan Pro, but the Duplicati plus B2 functionality and speed is superior.

2019-06-08 (10)

When the Unraid 6.7.0 release went public, I immediately updated, but soon realized my mistake, when several plugins stopped working. It took several weeks before plugin updates were released that restored full functionality. It is worth mentioning, again, that I find it strange that Unraid without community provided plugins is really not that usable, but the functionality still remains in community provided plugins, not in Unraid. Next time I will wait a few weeks for the dust to settle in the plugin community before updating.

Storage and disk management is reasonably easy, and much more flexible compared to hardware RAID management. But adding and removing disks is still mostly a manual process, and doing it without invalidating parity is very cumbersome and time consuming. At several times I gave up on the convoluted steps required to add or remove disks without invalidating parity, and just reconfigured the array and then rebuilt parity, hoping nothing goes wrong during the parity rebuild. This is in my opinion a serious shortcoming, maybe not in technology, but in lack of an easy to use and reliable workflow to help retain redundant protection at all times.

In order to temporarily make enough storage space in my secondary server, I removed all the SSD cache drives and replaced them with 12TB Seagate IronWolf drives. I did move all the data that used to be on the cache to regular storage, including the docker appdata folder. This should not be a big deal, but I immediately started getting SQLite DB corruption errors in apps like Plex, that store data in SQLite on the appdata share. After some troubleshooting I found many people complaining about this issue, that seems to have been exasperated by the recent Unraid 6.7.0 update. Apparently this is a known problem with the Fuse filesystem used by Unraid. Fuse dynamically spans shares and folders across disks, but apparently breaks file and file-region locking required by SQLite. The recommended workaround is to put all files that require locking to work on the cache, or on a single disk, effectively bypassing Fuse. If it is Fuse that breaks file locking behavior, I find it troubling that this is not considered a critical bug.

I am quite familiar with VM snapshot management using Hyper-V and VMWare, it is a staple of VM management. In Unraid I am using a Docker based Virt-Manager, which seems far less flexible, but more importantly, fails to take snapshots of UEFI based VM’s. Apparently this is a known shortcoming. I have not looked very hard for alternatives, but this seems to be a serious functional gap compared to Hyper-V or VMWare’s snapshot capabilities.

2019-06-05 (2)

As I started using the SMB file shares, now hosted on Unraid, in my regular day to day activities, I noticed that under some conditions the write speed becomes extremely slow, often dropping to around 2MB/s. This seems to happen when there are other file read operations in progress, and even a few KB/s of reads can drastically reduce the array SMB write performance. Interestingly the issue does not appear to affect my use of rsync between Unraid servers, but only SMB. I did find at least one other recent report of similar slowdowns, where only SMB is affected.

Since the problem appeared to be specific to Unraid SMB, and not general network performance, I compared the Unraid SMB performance with Windows SMB in a W2K19 VM running on the same Unraid system. By running W2K19 as a VM on the same Unraid system, the difference in performance will be mostly the SMB stack, not hardware or network.

On Unraid I created a share that is backed by the SSD cache array, that same SSD cache array holds the W2K19 VM disk image, so the storage subsystems are similar. I ran a similar test against an Unraid share backed by disk instead of cache.

I found a few references (1, 2) to SMB benchmarking using DiskSpd, and I used them as a basis for the test options I used. Start by creating a 64GB test file on all test shares, we reuse the file and it saves a lot of time to not recreate it every time. Note, we get a warning when creating the file on Unraid, due to SetFileValidData() not being supported by Unraid’s SMB implementation, but that should not be an issue.

>diskspd.exe -c64G \\storage\testcache\testfile64g.dat
WARNING: Could not set valid file size (error code: 50); trying a slower method of filling the file (this does not affect performance, just makes the test preparation longer)

>diskspd.exe -c64G \\storage\testmnt\testfile64g.dat
WARNING: Could not set valid file size (error code: 50); trying a slower method of filling the file (this does not affect performance, just makes the test preparation longer)

>diskspd.exe -c64G \\WIN-EKJ8HU9E5QC\TestW2K19\testfile64g.dat

I ran several tests similar to the following commandlines:

>diskspd -w50 -b512K -F2 -r -o8 -W60 -d120 -Srw -Rtext \\storage\testcache\testfile64g.dat > d:\diskspd_unraid_cache.txt
>diskspd -w50 -b512K -F2 -r -o8 -W60 -d120 -Srw -Rtext \\storage\testmnt\testfile64g.dat > d:\diskspd_unraid_mnt.txt
>diskspd -w50 -b512K -F2 -r -o8 -W60 -d120 -Srw -Rtext \\WIN-EKJ8HU9E5QC\TestW2K19\testfile64g.dat > d:\diskspd_w2k19.txt

For a full explanation of the commandline arguments see here. The test will do 50% read and 50% write, block sizes varied from 4KB to 2048KB, 2 threads, 8 outstanding IO operations, random aligned IO, warm up for 60s, run for 120s, disable local caching for remote filesystems.







From the results we can see that the Unraid SMB performance for this test is pretty poor. I redid the tests, this time doing independent read and write tests, and instead of various block sizes, I just did a 512KB block size test (I got lazy).



No matter how we look at it, the Unraid SMB write performance is still really bad.

I wanted to validate the synthetic tests results with a real world test, so I collected a folder containing around 65.2GB of fairly large files, on SSD, and copied the files up and down using robocopy from my Win10 system. I chose the size of files to be about double the size of the memory on the Unraid system, such that the impact of caching can be minimized. I made sure to use a RAW VM disk to eliminate any performance impact of growing a QCOW2 image file.

>robocopy d:\temp\out \\storage\testmnt\in /mir /fft > d:\robo_pc_mnt.txt
>robocopy d:\temp\out \\storage\testcache\in /mir /fft > d:\robo_pc_cache.txt
>robocopy d:\temp\out \\WIN-EKJ8HU9E5QC\TestW2K19\in /mir > d:\robo_pc_w2k19.txt

>robocopy \\storage\testmnt\in d:\temp\in /mir /fft > d:\robo_mnt_pc.txt
>robocopy \\storage\testcache\in d:\temp\in /mir /fft > d:\robo_cache_pc.txt
>robocopy \\WIN-EKJ8HU9E5QC\TestW2K19\in d:\temp\in /mir > d:\robo_w2k19_pc.txt

During the robocopy to Unraid I notice that sporadically the Unraid web UI, and web browsing in general, becomes very slow. This never happens while copying to W2K19. I can’t explain this, I see no errors reported in my Win10 client eventlog or resource monitor, I see no unusual errors on the network switches, and no errors in Unraid. I suspect whatever is impacting SMB performance is affecting network performance in general, but without data I am really just speculating.

The robocopy read results are pretty even, but again shows inferior Unraid SMB write performance. Do note that the W2K19 VM is still not as fast as my previous W2K16 RAID6 setup where I could consistently saturate the 1Gbps link for read and writes, on the same hardware and using the same disk.



It is very disappointing to discover the poor SMB performance, I reported my findings to the Unraid support forum, and I hope they can do something to improve performance, or maybe invalidate my findings.


Synology DS2411+ Performance Review

In my last post I compared the performance of  Synology DS1511+ against the QNAP TS-859 Pro. As I finished writing that post, Synology announced the new Synology DS2411+.
Instead of using a DS1511+ and DX510 extender for 10 disks, the DS2411+ offers 12 disks in a single device. The price difference is also marginal, DS1511+ is $836, the DX510 is $500, and the DS2411+ is $1700. That is a difference of only $364, and well worth it for the extra storage space, and the reliability and stability of all drives in one enclosure. I ended up returning my DX510 and DS1511+, and got a DS2411+ instead.

To test the DS2411+, I ran the same performance tests, using the same MPIO setup as I described in my previous post. The only slight difference was in the way I configured the iSCSI LUN; the DS1511+ was configured as SHR2, while the DS2411+ was configured as RAID6. Theoretically both are the same when all the disks are the same size, and SHR2 ends up using RAID6 internally.
iSCSI LUN configuration:

At idle the DS2411+ used 42W power, and under load it used 138W power. The idle power usage is close to the advertised 39W idle power usage, but quite a bit more than the advertised 105W power usage under load.

I use Remote Desktop Manager to manage all my devices in one convenient application. RDM supports web portals, Remote Desktop, Hyper-V, and many more remote configuration options, all in a single tabbed UI. What I found was that the Synology DSM has some problems when running in a tabbed IE browser. When I open the log history, I get a script error, and whenever I focus away and back on the browser window, the DSM desktop windows shift all the way to the left. I assume this is a DSM problem related to absolute and relative referencing. I logged a support case, and I hope they can fix it.
Script error:

Test results:

ATTO Write
CDM Read
CDM Write
PM810 267.153 260.839 256.674 251.850
DS2411+ 244.032 165.564 149.802 156.673
DS1511+ 244.032 126.030 141.213 115.032
TS-859 Pro 136.178 95.152 116.015 91.097


The DS2411+ published performance numbers are slightly better than the DS1511+ numbers, and my testing confirms that. so far I am really impressed with the DS2411+.

Synology DS1511+ vs. QNap TS-859 Pro, iSCSI MPIO Performance

Untitled Page I have been very happy with my QNap TS-859 Pro (Amazon), but I’ve run out of space while archiving my media collection, and I needed to expand the storage capacity. You can read about my experience with the TS-859 Pro here, and my experience archiving my media collection here.
My primary objective with this project is storage capacity expansion, and my secondary objective is improved performance.

My choices for storage capacity expansion included:

  • Replace the 8 x 2TB drives with 8 x 3TB drives, to give me 6TB of extra storage. The volume expansion would be very time consuming, but my network setup can remain unchanged during the expansion.
  • Get a second TS-859 Pro with 8 x 3TB drives, to give me 18TB of extra storage. I would need to add the new device to my network, and somehow rebalance the storage allocation across the two devices, without changing the file sharing paths, probably by using directory mount points.
  • Get a Synology DS1511+ (Amazon) and a DX510 (Amazon) expansion unit with 10 x 3TB drives to replace the QNap, to give me 12TB of extra storage, expandable to 15 x 3TB drives for 36TB of total storage. I will need to copy all data to the new device, then mount the new device in place of the old device.

I opted for the DS1511+ with one DX510 expansion unit, I can always add a second DX510 and expand the volume later if needed.
As far as hard drives go, I’ve been very happy with the Hitachi Ultrastar A7K2000 2TB drives I use in my workstations and the QNap, so I stayed with the larger Hitachi Ultrastar 7k3000 3TB drives for the Synology expansion.

For improving performance I had a few ideas:

  • The TS-859 Pro is a bit older than the DS1511+, and there are newer and more powerful QNap models available, like the TS-859 Pro+ (Amazon) with a faster processor, or the TS-659 Pro II (Amazon) with a faster processor and SATA3 support, so it not totally fair to compare the TS-859 Pro performance against the newer DS1511+. But, the newer QNap models do not support my capacity needs.
  • I use Hyper-V clients and dynamic VHD files located on an iSCSI volume mounted in the host server. I elected this setup because it allowed me great flexibility in creating logical volumes for the VM’s, without actually requiring the space to be allocated. In retrospect this may have been convenient, but it was not performing well in large file transfers between the iSCSI target and the file server Hyper-V client.
    For my new setup I was going to mount the iSCSI volume as a raw disk in the file server Hyper-V client. This still allowed me to easily move the iSCSI volume between hosts, but the performance will be better than fixed size VHD files, and much better than dynamic VHD files.
    Here is a blog post describing some options for using iSCSI and Hyper-V.
  • I used iSCSI thin provisioning, meaning that the logical target has a fixed size, but the physical storage only gets allocated as needed. This is very convenient, but turned out to be slower than instant allocation. The QNap iSCSI implementation is also a file-level iSCSI LUN, meaning that the iSCSI volume is backed by a file on an EXT4 volume.
    For my new setup I was going to use the Synology block-level iSCSI LUN, meaning that the iSCSI volume is directly mapped to a physical storage volume.
  • I use a single LAN port to connect to the iSCSI target, meaning the IO throughput is limited by network bandwidth to 1Gb/s or 125MB/s.
    For my new setup I wanted to use 802.3ad link aggregation or Multi Path IO (MPIO) to extend the network speed to a theoretical 2Gb/s or 250MB/s. My understanding of link aggregation turned out to be totally wrong, and I ended up using MPIO instead.

To create a 2Gb/s network link between the server and storage, I teamed two LAN ports on the Intel server adapter, I created a bond of the two LAN ports on the Synology, and I created two trunks for those connections on the switch. This gave me a theoretical 2Gb/s pipe between the server and the iSCSI target. But my testing showed no improvement in performance over a single 1Gb/s link. After some research I found that the logical link is 2Gb/s, but that the physical network stream going from one MAC address to another MAC address is still limited by the physical transport speed, i.e. 1Gb/s. This means that the link aggregation setup is very well suited to e.g. connect a server to a switch using a trunk, and allow multiple clients access to the server over the switch, each at full speed, but it has no performance benefit when there is a single source and destination, as is the case with iSCSI. Since link aggregation did not improve the iSCSI performance, I used MPIO instead.

I set up a test environment where I could compare the performance of different network and device configurations using readily available hardware and test tools. Although my testing produced reasonably accurate relative results, due to the differences in environments, it can’t really be used for absolute performance comparisons.

Disk performance test tools:

Server setup:

Network setup:

  • HP ProCurve V1810 switch, Jumbo Frames enabled, Flow Control enabled.
  • Jumbo Frames enabled on all adapters.
  • CAT6 cables.
  • All network adapters connected to the switch.

QNap setup:

Synology setup:

To test the performance using the disk test tools I mounted the iSCSI targets as drives in the server. I am not going to cover details on how to configure iSCSI, you can read the Synology and QNap iSCSI documentation, and more specifically the MPIO documentation for Windows, Synology and QNap.
A few notes on setting up iSCSI:

  • The QNap MPIO documentation shows that LAN-1 and LAN-2 are in a trunked configuration. As far as I could tell the best practices documentation from Microsoft, DELL, Synology, and other SAN vendors, say that trunking and MPIO should not be mixed. As such I did not trunk the LAN ports on the QNap.
  • I connected all LAN cables to the switch. I could have done direct connections to eliminate the impact of the switch, but this is not how how I will install the setup, and the switch should be sufficiently capable of handling the load and not add any performance degradation.
  • Before trying to enable MPIO on Windows Server, first connect one iSCSI target and map the device, then add the MPIO feature. If you do not have a mapped device, the MPIO iSCSI option will be greyed out.
  • The server’s iSCSI target configuration explicitly bound the source and destination devices based on the adapters IP address, i.e. server LAN-1 would bind to NAS LAN-1, etc. This ensured that traffic would only be routed to and from the specified adapters.
  • I found that the best MPIO load balance policy was the Least Queue Depth Option.

During my testing I encountered a few problems:

  • The DX510 expansion unit would sometimes not power on when the DS1511+ is powered on, or would sometimes fail to initialize the RAID volume, or would sometimes go offline while powered on. I RMA’d the device, and the replacement unit works fine.
  • During testing of the DS1511+, the write performance would sometimes degrade by 50% and never recover. The only solution was to reboot the device. Upgrading the the latest 3.1-1748 DSM firmware solved this problem.
  • During testing of the DS1511+, when one of the MPIO network links would go down, e.g. I unplug a cable, ghost iSCSI connections would remain open, and the iSCSI processes would consume 50% of the NAS CPU time. The only solution was to reboot the device. Upgrading the the latest 3.1-1748 DSM firmware solved this problem.
  • I could not get MPIO to work with the DS1511+, yet no errors were reported. It turns out that LAN-1 and LAN-2 must be on different subnets for MPIO to work.
  • Both the QNap and Synology exhibits weird LAN traffic behavior when both LAN-1 and LAN-2 is connected, and the server generates traffic directed to LAN-1 only. The NAS resource monitor would show high traffic volumes on LAN-1 and and LAN-2, even with no traffic directed at LAN-2. I am uncertain why this happens, maybe a reporting issue, maybe a switching issue, but to avoid it influencing the tests, I disconnected LAN-2 while not testing MPIO.

My test methodology was as follows:

  • Mount either the QNap or Synology iSCSI device, power of the other device while not being tested.
  • Connect the iSCSI target using LAN-1 only and unplug LAN-2, or connect using MPIO with LAN-1 and LAN-2 active.
  • Run all CDM tests with iterations set at 9, and a 4GB file-set size.
  • Run ATTO with the queue depth set to 8, and a 2GB file-set size.
  • As a baseline, I also tested the Samsung PM810 SSD drive using ATTO and CDW.

Test result summary:

ATTO Write
CDM Read
CDM Write
Total (MB/s)
PM810 267.153 260.839 256.674 251.850 1,036.516
DS1511+ MPIO 244.032 126.030 141.213 115.032 626.307
TS-859 Pro MPIO 136.178 95.152 116.015 91.097 438.442
DS1511+ 122.294 120.172 89.258 105.618 437.342
TS-859 Pro 119.370 99.864 76.529 89.752 385.515


Detailed results:
Atto.P810 CDM.P810
DS1511+ MPIO:
Atto.Synology.MPIO CDM.Synology.MPIO
TS-859 Pro MPIO:
Atto.Qnap.MPIO CDM.Qnap.MPIO
Atto.Synology CDM.Synology
TS-859 Pro:
Atto.Qnap CDM.Qnap

Initially, I was a little concerned about the DX510 being in a separate case connected with an eSATA cable to the main DS1511+. Especially after I had to RMA my first DX510 because of what appeared to be connectivity issues. I was also concerned that there would be a performance difference between the 5 drives in the DS1511+ and the 5 drives in the DX510. Testing showed no performance difference between a 5 drive volume and a 10 drive volume, and the only physically noticeable difference was that the drives in the DX510 ran a few degrees hotter compared to the drives in the DS1511+.

As you can see from the results, the DS1511+ with MPIO performs really very well. Especially the 244MB/s ATTO read performance that gets close to the theoretical maximum of 250MB/s over a 2Gb/s link.

But technology moves quickly, and as I was compiling my test data for this post, Synology released two new NAS units, the DS3611xs and the DS2411+. The DS2411+ is very appealing, it is equivalent in performance to the DS1511+, but supports 12 drives in the main enclosure.
I may just have to exchange my DS1511+ and DX510 for a DS2411+…

[Update: 25 July 2011]
I returned the DS1511+ and DX510 in exchange for a DS2411+.
Read my performance review here.