June 14, 20242 yr Hi, I have several ssds that are to be added to an ssd pool. I did a perf test on them to see if I had any slow disks...and uhhh...it seems I have some VERY slow ssds. They start off writes around 500MB/s+ but then get down to 20MB/s or lower after a bit. I realize there is some slowdown expected but this is very slow and it's not across all disks. Some of my oldest, cheapest disks have no issue sustaining writes of over 100MB/s, any ideas? Attached the full output and the script used to test the devices, along with a screenshot of the device IDs and models so you can see which drives are so slow. Thanks for your thoughts. ssd_perf_test.sh perf_results.txt
June 14, 20242 yr Community Expert Most SSDs cannot sustain high write speed, though 20MB/s seems really low, but using dd to test may not always be reliable, try an actual copy test, with large files, if the same it's the device.
June 15, 20242 yr Author Thanks. Yeah I just spun up 4 ssds in a zfs raid 0 and rsync’d a 175GB file. Average speed was 22.9MB/s. crazy. Something seems wrong. The ssds are connected via E-Sas using the card below. This goes to a sas controller in an external enclosure over 2ft esas cables Card https://a.co/d/b7Y8gwM External enclosure, inside of another box. https://a.co/d/fOXyRY4 Edited June 15, 20242 yr by geeksheikh
June 15, 20242 yr Community Expert Try with other 4, or just a single one, different model ideally, if you get the same it's probably not the SSDs.
June 19, 20242 yr Author Gonna do some testing with the SAS connections. Perhaps I have a bad cable or rail or setup. Will double check. Here's a pretty telling story
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