October 20, 20169 yr Hi! I've built my first Unraid machine 2 days ago. It will serve as NAS (maybe in future I will do something more with it). The hardware: CPU: AMD X4 845 RAM: 8GB non-ECC Motherboard: ASROCK A88M-G/3.1 FM2 A88X Cache SSD: Adata SP580 128GB Pool of 4 drives: Parity: 4TB (WD Red) HDDs: 1TB, 2TB and 4TB. My copying from the Unraid to my Windows machines works at full speed. I have a problem with copying files to Unraid. At the beginning the speed is at around 100-110MB/s which is my max speed of the network, but after few gigs of data it drops to zero then it hovers around 30-40MB/s. I'm copying mostly large files. From SSD to SSD Cache. The example in the gif I attached is 10GB, where there are two 4.4GB files, two 400MB files, and few small files (less than 200MB in total, and those were copied at the very end). Same thing is happening on two Windows 10 machines. I've found a post suggesting to disable Large Send Offload V2, but that didn't help. I've also attached diagnostics files straight after I copied the files from gid. Thank you in advance for all the help! nas-diagnostics-20161020-1012.zip
October 20, 20169 yr Looks like the caching is working initially then as it gets full the transfer slows down, I think that is expected behaviour. Sent from my LG-H815 using Tapatalk
October 20, 20169 yr Author Looks like the caching is working initially then as it gets full the transfer slows down, I think that is expected behaviour. Sent from my LG-H815 using Tapatalk That is not the case. Before I started copying I made sure the cache is free (whole 120GB).
October 20, 20169 yr It's not the cache disk I'm referring to, it's the write cache which I think uses RAM Sent from my LG-H815 using Tapatalk
October 20, 20169 yr Author It's not the cache disk I'm referring to, it's the write cache which I think uses RAM Sent from my LG-H815 using Tapatalk I see. While I was copying I checked Memory usage in System Status and it was staying at around 10-15%. Also that would indicate that the Cache SSD can't handle 100MB/s sequential write, which seems unlikely. I guess I can stop the arrey, shut down the machine and put it in my WS to run benchmarks. Any other possibilities?
October 20, 20169 yr Community Expert Make sure files are actual being written to cache, if yes, it probably needs trimming. If writing to the protected array using the default write method speed looks normal, initial higher speed is due to RAM caching. You can increase write speed by enabling turbo write, but all disks will spin up for writes. Settings -> Disk settings -> Tunable (md_write_method): reconstruct write
October 20, 20169 yr Are you sure that what you're copying is going to the cache disk first? Not straight to the protected array? Sent from my LG-H815 using Tapatalk
October 20, 20169 yr Author Make sure files are actual being written to cache, if yes, it probably needs trimming. If writing to the protected array using the default write method speed looks normal, initial higher speed is due to RAM caching. You can increase write speed by enabling turbo write, but all disks will spin up for writes. Settings -> Disk settings -> Tunable (md_write_method): reconstruct write I have cache enabled for the share and after copying I can see that on cache disk there is 10GB Used. About trimming - I'd think that it's enabled by default. Where can I check it? I don't see such an option in settings.
October 20, 20169 yr Community Expert Trim is not enable by default, install the Dynamix plugin and set a schedule for it, usually once a day is enough. http://lime-technology.com/forum/index.php?topic=36543.0 You can also do it manually at any time by running: fstrim -v /mnt/cache
October 20, 20169 yr Author Trim is not enable by default, install the Dynamix plugin and set a schedule for it, usually once a day is enough. http://lime-technology.com/forum/index.php?topic=36543.0 You can also do it manually at any time by running: fstrim -v /mnt/cache Oct 20 15:00:19 NAS root: /mnt/cache: 110 GiB (118042435584 bytes) trimmed It didn't help.
October 20, 20169 yr Community Expert Enable turbo write and copy direct to the array, if speed is better disable cache (or get a faster SSD).
October 20, 20169 yr Author Enable turbo write and copy direct to the array, if speed is better disable cache (or get a faster SSD). I've attached the SSD benchmark. I thought that in this application sequential writes is what is importnat. Am I wrong? About Turbo Write is this the right function: Tunable (md_write_method): "reconstruct write"?
October 20, 20169 yr Community Expert Benchmarks and real usage speeds are often different, although I would expect that SSD to be able to sustain writes close to 100MB/s. Yes, to enable turbo write change mode to "reconstruct write", disable cache for that share and test, if speed is better you know the problem is the SSD.
October 20, 20169 yr Author Benchmarks and real usage speeds are often different, although I would expect that SSD to be able to sustain writes close to 100MB/s. Yes, to enable turbo write change mode to "reconstruct write", disable cache for that share and test, if speed is better you know the problem is the SSD. Hm... OK, it's better, not by much, there is no more 100MB/s at the beginning, it starts slower, but than has a more consistant speed of 55-75MB/s. I'm think if it's worth the upgrade. Now I have 8TB of data to migrate, but later I will be having 10-30GB of data at time to store...
October 20, 20169 yr Community Expert Turbo write can only write as fast as your slowest disk, you have a older WD 1TB Green slowing you down, with all newer disks it would write at or close to gigabit.
October 20, 20169 yr Author Turbo write can only write as fast as your slowest disk, you have a older WD 1TB Green slowing you down, with all newer disks it would write at or close to gigabit. I have two more 4TB Red and one 2TB Red comming (I have to migrate the data first). Thank you for troubleshooting this, I will think over my options.
October 20, 20169 yr I think this might be the SLC / TLC caching of the drive. A 120GB SSD will have a smaller write cache and I understand the SP580 doesn't have any onboard DRAM. This might be normal behaviour for this SSD for sequential writes.
October 23, 20169 yr Author OK, so I returned the Adata 120GB SSD and bought Samsung 850 EVO 250GB and the problem is solved. Thank you again for all the help!
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