SATA SSD's - Are Disk Scrub and Disk Test necessary?

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jimk1963 wrote:

 

Question: with SATA SSD's, is it advisable or not advisable to run all 4 of these maintenance tasks on this schedule? I've read that Disk Test and Disk Scrub in particular can shorten an SSD's life, but seems anecdotal. 

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SSDs all have a limited number of writes cycles ("endurance").

 

The Disk Test only does reads (running the smartctl long test), so that will not shorten the SSD life.  

 

The Disk Scrub is a combination of a mdadm scrub and a btrfs scrub.  The man page for btrfs scrub suggests that it only writes to repair errors.  That is not something I've tried to confirm. As far as the mdadm scrub goes, I think that is verifying the parity blocks (and only rewriting ones that are wrong).  But it is possible that it is actually recomputing and rewriting all the partity blocks.  

 

 

 

 

 

 

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jimk1963 wrote:

RN528X, freshly repopulated with 8 Crucial 4TB MX500 SATA SSD's. 

 

With guidance from StephenB , I set up the NAS to perform each of the 4 Maintenance tasks once per quarter (Scrub, Disk Test, Defrag, Balance). This was with spinning HDD's initially.

 

Question: with SATA SSD's, is it advisable or not advisable to run all 4 of these maintenance tasks on this schedule? 

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is there anything "electromechanical" about the HDD's that makes them need these tests but SSD's do not?

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Getting back to the main questions: 

 

• Defrag has marginal value even with mechanical disks.  SSDs have 0 seek time, so you could just turn this off.  You can always run it manually.
• I'd run the disk test, as it doesn't effect endurance.
• Balance reclaims/consolidates optimizes BTRFS free space.  It will do some writes, but I'd run it anyway.  On my systems, it usually completes in less than 45 minutes.
• Scrub is the unknown.  If it does rewrite all the parity blocks (which would be the worst case), then you'd be writing 25% of each disk with RAID-6, and 12.5% of each disk with RAID-5.  Assuming RAID-6, you'd be writing 1 TB per drive every time you run it.  The endurance rating for the MX500 4 TB model is 1000 TB.  Overall the effect is relatively small (less than 0.4% reduction in disk life per year).  I'd probably choose to run it, but I guess you could reduce the frequency.