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reconstructive write does not spin up disks

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I am in the middle of transferring TBs of data to my new Unraid NAS. I have reconstrive write set and it seems to work. But every once in a while I discover spun down discs and slower write performance. It was my impression that when reconstructive write is enabled every write should spin up all disks. Any idea?




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I do but: That plugin also claims "reconstructive write" active. I set the number of disks to maximum (so it should never kick in and reduce it). And in order to make sure it does not fiddle with it I disabled it.


The setting under Disk settings does still show 

md_write_method = reconstruct write


and the plugin is disabled.



Still believe me: After a while disks are spun down and I do see reads only from the spun up disks. Once I manually spin all disks up things are back to normal. VERY confusing.


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Can't remember since which OS version, even you set reconstruct write, if multiple session write to array or file cross allocation to different disk, it will change to R/M/W and back.


So you should review file allocation setting.

Edited by Vr2Io
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Yes concurrent reads will trigger RMW and it can switch back and forth between both many times a second... but I've never seen that scenario causing drives to go to sleep, it should only happen when things are being quite hammered so they'd be needed... but maybe I just don't have enough drives to see that.

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22 minutes ago, Kilrah said:

but I've never seen that scenario causing drives to go to sleep

Agree. But may be some situation keeping in R-M-W long enough.... anyway haven't test or try to reproduce.


Does OP use parity, reconstruct write only have meaning with parity. Just to be confirm, or provide screenshots / diagnostic.

Edited by Vr2Io
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6 data disks plus 2 parity


Currently 90-100 MB/sec constant writes (which is why I want reconstructive write to stay on). 🙂 


I currently set "spin down" to never for the time being and keep filling up to drives. Will try to reproduce in 1-2 weeks and if I can reproduce it will send diagnostics here.


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