unRaid 6

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TuxDude

Well-Known Member
Sep 17, 2011
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I was under the impression that if you disable copy-on-write (which I have for my vdisks share stored on the cache pool) that any performance issues are mitigated for the most part. I'm not worried about the data integrity of my VMs as they are not mission critical.
Disabling Copy-on-Write (CoW) does help a lot with the performance impact, though at the current stage of BTRFS development performance is still not a priority and so it still won't perform as well as most other filesystems. The other side-effect of disabling CoW is that it also disables BTRFS's checksumming for those files - so you're left with files that are no better protected than eg. ext4 and perform worse. If you're taking advantage of BTRFS's other features (snapshots, subvolumes, multiple-devices, etc.) then maybe there's a reason to stick with it, but I usually recommend using other filesystems for VM disks.
 

EffrafaxOfWug

Radioactive Member
Feb 12, 2015
1,394
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The other side-effect of disabling CoW is that it also disables BTRFS's checksumming for those files - so you're left with files that are no better protected than eg. ext4 and perform worse
Yoiks! I wasn't aware of this and it seems like a glaring design issue but checking the FAQ you're quite right. Cheers for the pointer as I was mulling setting up a no-COW partition for some VM images.
 

RodyMcAmp

New Member
Mar 21, 2013
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I won't touch unRAID.

FreeNAS - YES!
Proxmox - Sure
Ubuntu/ CentOS - Of course
Napp-IT - ok (but I wish it was ZoL based!)
napp-it works on ZOL or at least it did a year ago. I never tried it, I was using open indiana when i was using Napp-it