August 8, 20196 yr I just started with Unraid and love it so far. Moved from FreeNAS because it was unstable. So far Unraid is rock stable. I have a question about were to use my SSD. I see that it's recommended to have it as a cache drive. My server has to 2TB WD RED NAS drives and one 120GB SSD. I've tested both with and without my SSD as cache and the write speed are approximately the same (1gigabit ethernet). I'm planning to run some VMS on the SSD. I just wonder if there's any point in having the SSD as cache, or should I use it as a disk in my array and create a VM share? Does it hurt the SSD to have it in the array vs as a cache device?
August 8, 20196 yr Reasons to NOT use a SSD in the array: it is not officially supported to have a SSD as part of the array Trim is not supported for array devices so SSD performance is likely to degrade over time array write performance is determined by the slowest drive involved in the write so often no performance benefit. if you want to use VMs you want a drive that is NOT part of the array to maximise performance. most people use a SSD either as part of the cache pool or mounted via the Unassigned Devices (UD) plugin for these reasons.
August 8, 20196 yr TRIM is turned off in the array so for SSD, it's almost always better to use it in the cache pool where write performance is important (e.g. VM vdisk, docker, appdata etc.). The Unraid cache pool has evolved to being pretty essential for a full experience with Unraid so you should have a cache disk anyway.
August 8, 20196 yr 1 hour ago, BenjaminK said: My server has to 2TB WD RED NAS drives and one 120GB SSD. I've tested both with and without my SSD as cache and the write speed are approximately the same Do you have a parity drive? If not that would be why no difference. Are you writing to a cached user share? If not that would be why no difference.
August 8, 20196 yr Author 3 minutes ago, trurl said: Do you have a parity drive? If not that would be why no difference. Are you writing to a cached user share? If not that would be why no difference. Caching was enabled on the share. I think my network connection is to slow, and I was testing with big files only. Not many small files. Should probably use a testing tool next time 🙂 I've changed the SSD to cache now. Unraid just need 4 hours to Parity-Sync 🙂 Edited August 8, 20196 yr by BenjaminK
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