I'm currently juggling drives on my NAS.  Since I have multiple different models of drives, and I want to access my array shares faster, I intend to change the drives to shares that I rarely use.  And I also want to change 1 into my parity drive.  Will it impact performance when writing?  

For standard hdd’s, no.


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Yes, Standard sdd, just that they are sata 2.  Will be using my sata 3 parity drive on shares that I access all the time.  To get faster read.

UnRAID does not support SSD’s in the array. So your parity and data drives should be standard platter hard drives. The SATA II spec is 300MB/s. But a platter drive cannot reach that speed. So SATA II will be more than adequate for all data/parity drives.

Cache drives/pools on the other hand should be set up using SSD’s because of their speed. And they are supported in unRAID for this purpose. SATA III spec is 600MB/s, and SSD’s can get close or reach these speeds so SSD’s should be on SATA III controllers.

Note: these are specified speeds and not actual speeds in real world application accounting for overhead. But it’s late and I’m typing this on mobile.


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Understood.  I didn't know that Unraid didn't support SSD on array.  What about SAS SSDs?  Do they support on the array?

No.  It isn't an issue of SATA vs SAS.  It has to do with the way SSD's work and the unRAID OS keeping track of where the data is located on the SSD.  I recommend searching more about SSD's on the array.  Now, keep in mind that some people have used SSD's on the array.  But, if you have problems, unRAID has been clear that it is not supported.

 

As for SSD's on SAS for cache, SAS2008 doesn't support TRIM.  So, you want the SSD cache drives on a SATA III controller.  I've used a couple different SATA III PCIe cards.  This 2 port SATA III card (SY-PEX40039) is in my current unRAID server for by cache pool and works great.  It supports TRIM.  Although, you might get errors the first two times TRIM runs.  The trick is to force TRIM to run two or three times.  After that, no issues.  Also, keep in mind that when there are errors, it can sometimes be a bad SATA cable.  Or the cable is not seated cleanly at the drive or controller.  I would just make sure the cables are connected properly when installing, and then run TRIM two or three times.  If after that you get errors on one or both drives, then consider replacing the cables.  Personally, I recommend these cables because I find they put little to no tension/torque on the drive or conroller.

 

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