Hello together,

my Unraid Server has very Slow Write Speeds.

When i copy a file to my Cache drive bond it start's with 120mb/s. After seconds it is only by 20mb/s.

The Unraid System is very slow (Webinterface) at the copy process.

 

Does anybody know the reason?

Thanks.

It’s a known issue that using the btrfs cache pool as opposed to using single cache in xfs degrades cache performance, but I’ve never seen speeds that low.

 

The initial speed of 120MB/s is Unraid caching to RAM, this suggests to me that the network is working fine, if you copy directly to a disk share or uncached share is the speed same or better?

 

thank you for your answer.

When i copy to the unraid array (not to the cache pool) i've got write speeds around 16mb/s.

 

I don't know wheres the Problem.

On WebGUI go to: tools > diagnostics and post complete zip

here the diagnostic file.

 

Download

here the diagnostic file.

 

Download

Please don't use unknown hosting sites for this. You can usually attach the diagnostics in the forum unless it is very large.

hey guys,

now i've checked some things.

First i've disabled one of the cache ssd's. Then i have converted the other SSD to the XFS Filesystem.

The result is the same. Low write speeds.

 

After that i tested a WF green 1,5TB as the cache drive with the XFS file System.

The result is great. Full Gigabit file transfers.

 

See the attachment.

What are the Problems with the samsung SSD Pro?

 

Thanks and nice greetings

It would be interesting to see the temperature of the drive as well. You can change the Tunable (poll_attributes) temporarily to a low number say 180 (3 minutes) and see what readings you get when copying a lot of data to it. Would be good to understand if its overheating or not.

i've copy a big file to one of the ssd.

I touched the ssd. The ssd is cold.

 

The speed is low.

ok, now with poll_attributes =180

The temperature is measured on the chip so it heats up much faster than the case. I have seen this on the 840 EVO but it doesn’t necessarily mean that your drive behave the same way. Just wanted to take one possible parameter out of the equation 

 

I use 2 of the Samsung SSD 850 Pro 1TB.

You can try connecting the SSD to a win PC and run a benchmark like AS SSD Benchmark and see if writes are normal.

I'm also having the same problem after upgrading to 6.1.4.

 

i started this tread cause i wasn't sure what the issue was:  https://lime-technology.com/forum/index.php?topic=44185.0

 

but its definitely related to the cache drive.  i cant even get a simple dd to finish:

root@Tower:/mnt/cache# dd if=/dev/zero of=5g bs=1M count=5000
<ctrl-c>
314+0 records in
314+0 records out
329252864 bytes (329 MB) copied, 424.714 s, 775 kB/s

 

also using a samsung SSD

Device Model: Samsung SSD 840 EVO 500GB

 

the dd works just fine on my regular drives (albeit a bit slow, but it actually finishes as expected):

root@Tower:/mnt/user/tmp# dd if=/dev/zero of=speedtest1 bs=1M count=5000
5000+0 records in
5000+0 records out
5242880000 bytes (5.2 GB) copied, 154.794 s, 33.9 MB/s

 

 

I just ordered another 960GB SSD, will see how the performance improves with the new drive.

 

Hey guys,

 

i've found the solution on my HP ML310e Unraid Server.

 

I've connected the 2 Samsung SSD Pro 1TB to the Onboard Controller.

The Onboard Controller has two 6G Ports.

 

The other WD RED HDDs are connected to the LSI Controller with IT firmware.

Now it looks that everything works fine.

 

Thank you.

unfortunately i dont think this would be the same solution for me, nothing has changed for me before/after the upgrade.  I will update once i receive the new drive.

I'm experiencing the same issue with two new Samsung 850 SSDs in a cache pool.  With the cache enabled, writes max out at about 25MB/s.  Without cache, writes average 75MB/s and max at 110MB/s (straight to the array without SSDs).

 

I'm a new customer that just purchased unRaid with the intention of using the cache pool feature.  This is a little disappointing.

Wait, 120mb/s is slow? I'm sitting at 11.5mb/s consistent. D:

Wait, 120mb/s is slow? I'm sitting at 11.5mb/s consistent. D:

 

25MBps is slow considering the SSD cache pool should max out the gigabit network interface at 125MBps.

Wait, 120mb/s is slow? I'm sitting at 11.5mb/s consistent. D:

 

120 MB/s is not slow, it's about the max you can expect out of a 1 GigE connection.

11.5 MB/s is about the max you can expect out of a 100 Mb/s connection. Make sure your adapter is capable of Gigbit speeds, and then make sure you don't have any bad wires or non-Gigbit capable switches/routers along the way that are the bottle neck.

 

Your problem appears to be related to network issues, where the OP problem seems to be disk / filesystem related since it starts out at a decent speed then slows down once the initial "cached" write is exceded.

 

So if the OP was just writing small files I wouldn't expect him to notice this slow down. I am not sure what is slowing down your writes...

 

Do you ever TRIM your SSD?

 

Also just to be clear, your prob not going to get actual 125Mbps, due to packet overhead. But you should get much closer then 25Mbps.

I'm experiencing the same issue with two new Samsung 850 SSDs in a cache pool.  With the cache enabled, writes max out at about 25MB/s.  Without cache, writes average 75MB/s and max at 110MB/s (straight to the array without SSDs).

 

I'm a new customer that just purchased unRaid with the intention of using the cache pool feature.  This is a little disappointing.

 

I can sustain gigabit speed writing to my cache pool of two Samsung 840 EVO.

 

Maybe try a different controller, like the OP.