Hello Community,

 

I am new to unraid and just setup a (looking to the forum pretty small) unraid setup. The transfer speed is slow, way slower than expected (I get around 54 MB/s). Therefore, I have two questions:

1. Is my expectation (see below) wrong?
2. If not: Where is the bottleneck?

 

My setup and what I expect

 

Network:

• I use Gigabit Ethernet, which limits the transfer rate to around 936 Mbit/s = 117 MB/s

 

Computer

• I use a refurbed Lenovo ThinkCentre M900
• CPU: Intel Core i5-6600T @ 2,70GHz
• RAM: 16 GB DDR4
• The CPU load in the dashboard is around 12-30 % during transfer, so it does not seem to be a problem?

 

Disks (both via USB 3)

• Currently no cache (fix one problem at a time)
• Disk 1: Seagate IronWolf 4TB, 5400 U/min
  • CMR, Max. Sustained Transfer Rate OD (MB/s) 202 MB/s
  • Write speed shoudl be somewhere above 150 MB/s? Is that realistic?
  • Connected via a SABRENT USB-HD Docking station
    •  They state 5Gbps which is USB 3.0 speed, so it should not be the bottleneck?
• Parity: WD Elements Portable
  • 5400 U/min
  •   Write speed should be above 110 MB/s?

 

Disk Connection

• The disks are connected via USB 3.0 with 5GBits/s. That should be around 450 MB/s in practice.
• The ThinkCentre has plenty of these ports, but unfortunately only one USB 3.0 Controller. So I guess the speed needs to be shared across all devices? The Unraid USB stick should not take buch, so still 200 MB/s should be available per USB disk.

 

root@x:~# lsusb -t
/:  Bus 02.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/10p, 5000M
    |__ Port 3: Dev 2, If 0, Class=Mass Storage, Driver=usb-storage, 5000M
    |__ Port 4: Dev 3, If 0, Class=Mass Storage, Driver=usb-storage, 5000M
    |__ Port 5: Dev 4, If 0, Class=Mass Storage, Driver=usb-storage, 5000M
/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/16p, 480M

 

With this, I would expect a write speed to the NAS of about 110 MB/s or more, with the WD Elements portable hdd being the limit.

 

 

Finding the bootleneck

 

In practice, I only get 54 MB/s when sending data (files of around 600 MB each) to the NAS vie the Windows Explorer and a SMB share.

I tried to test the disk speed with the DiskSpeed container from the "Apps" tab, but that just does not work. When I click on "Benchmark Drives" and leave the default settings, I just get an empty window and no results. Unfortunately, I could not fix that. Are ther alternative ways?

What else should I test?

 

Thanks in advance for help!

 

34 minutes ago, DennisBbg said:

Parity: WD Elements Portable

Is this a 2.5" or 3.5" disk? If 2.5" it will be SMR.

 

Also note that USB is not recommended for array or pool devices, for various reasons, including performance.

4 hours ago, JorgeB said:

Is this a 2.5" or 3.5" disk? If 2.5" it will be SMR.

 

Thanks for the answer. It is 2.5". How much does this decrease the performance when transferring ~20 G in 600 MB files?

 

Thanks for that hint. I choose the USB devices because I did not want to spend hundrets of euros for now and this with the ThinkCentre seamed like a cheap but ok option.

Edited April 7, 20242 yr by RaidRover

I added the cache to the setup (internal SSD).

Unfortunately, the transfer speed only slightly increased to around 60 MB/s. At the same time, the CPU usage increased / has spikes (see image).

 

I tested the disk directly on my laptop. When writing the same data, it starts with around 500 MB/s, goes down to around 200 MB/s and very slowly goes further down to around 150 MB/s. So it seems that the bottleneck is somewhere else.

 

Is there something else I could test?

 

 

Edited April 7, 20242 yr by RaidRover

Start by running a single stream iperf test in both directions to confirm it's not a LAN issue.

13 hours ago, JorgeB said:

Start by running a single stream iperf test in both directions to confirm it's not a LAN issue.

 

Thanks! Actually the router seems to be one bottleneck; I can get around 700 MBits/s through it. When I add a switch connected to the router and both my laptop and unraid, iperf gives me around 800 MBit/s = 100 MB/s and explains part of the missing speed.

Unfortunately, the file transfer only got up to 80 MB/s, so 20 are still missing.

Edited April 8, 20242 yr by RaidRover

Hitting line speed with iperf and gigabit should be pretty easy, not hitting it means there's a LAN problem, and the actual speeds can then be slower than iperf, I suggest trying to fix that and it should help.

I now tried iperf3 via WSL, which gives me 929 MBit/s. Not optimal, but ok I guess?

I wonder why some windows binary is way slower (639 MBit/s).

The transfer speed with SMB is still stuck at 69 MB/s.

 

With another Laptop, this time Ubuntu 22.04, I tried again. iperf3 gives a transfer speed of 942 MBit/s, which seems good. However, the transfer speed  via SMB still is below 70 MB/s.

 

I also added a SSD Cache partition where the data is written to and the CPU has capacity.

Do you have further advice? Thanks in advance!

10 hours ago, RaidRover said:

I now tried iperf3 via WSL, which gives me 929 MBit/s. Not optimal, but ok I guess?

That would be OK, assuming a single stream iperf test, still, if the Windows explorer transfer graph still looks like the above, it still points to a network problem (or the client PC), when the network is not the issue, you see full speed for the first few seconds of a transfer, while its being cached to RAM, and if it slows after that then it would be the devices not being able to keep up with the required write speed.