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Forum Discussion
Volume Maintenance and Bit-rot
My NAS and usage may help with this question? NAS: RN626 Apps: Plex/Anti-Virus and Photo Hosting Weekly Backkups of two PCs's Files and images. Month adds of a few hundred photos/videos. Host...
NASguru wrote:
I presume if Bit-Rot isn't used than routine defragmentation wouldnt' be required?
Well, with any file system the need for defrag does depend on usage.
As far as BTRFS goes, updating a file in a share that has a snapshot will fragment that file. That happens even if bit-rot protection is off.
NASguru wrote:
I'm guessing the 626 is a lower end NAS since it wasn't on by default but even so I'm uncertain how much I would really need it.
The 626X is at the top of the line of course. Perhaps the manual needs a bit of updating.
Bit-Rot protection is a proprietary netgear feature. "Bit-Rot" occurs when files somehow get corrupted on the disk. The bit-rot protection uses the parity info plus the BTRFS file checksum to recover the file data. The odds of bit-rot on an RN626X are lower than most consumer-NAS because it uses error-correcting RAM.
Enabling Bit-Rot protection also enables CoW all the time.
NASguru wrote:
So I'm curious to what if any recommendation exists for setting up Volume Maintenance?
I did manage to find this post but wasn't sure how model and usage dependent those recommendations are: https://community.netgear.com/t5/Using-your-ReadyNAS/Readynas-3220-What-is-recommended-volume-maintenance-schedule/m-p/1022420#M100585
Personally I run each of the 4 tests once a quarter, spacing them out through the quarter.
That's good feedback as usual. I believe you have a 526 so do you use Bit-rot and if so was there a significant performance hit? I didn't have it turned on when I moved all my data to the new NAS and from what I read it would only help with new files written to the NAS. So I guess the protection would be limited? As for the other tests, I was going to run the defrag/balance twice a month and the scrub (which takes forever) 3 times a year. I dont' really know what the disk test does or if it's necessary as their is no explaination given in the manual.
NASguru wrote:
That's good feedback as usual. I believe you have a 526 so do you use Bit-rot and if so was there a significant performance hit?
It's not turned on in my RN102 and RN202 (both are jbod, so it doesn't really apply). The RN526 isn't really set up yet - I'm still kicking the tires on it. It's on at the moment, and I'm planning to leave it on.
NASguru wrote:
I didn't have it turned on when I moved all my data to the new NAS and from what I read it would only help with new files written to the NAS. So I guess the protection would be limited?
It should work on all the files in the shares where it's turned on (even if it is turned on after files are written to the share).
NASguru wrote:
I dont' really know what the disk test does or if it's necessary as their is no explaination given in the manual.
I believe its the long non-destructive SMART test (built into the drive).
Got it on Bit-rot and I intend to do some testing here using a dummy share and files to see what if any hit the 626 takes. I'm sure there is some degration but I'm still not convinced it's needed given my use. Although, if the performance hit is negligible I may just leave it on for added insurance. Especially on files that are rarely accessed such as old pictures/videos. You wouldn't happen to know how long that disk test runs? It probably varies per disk and array size but just ballpark would be enough of an idea. I'm unable to run it manually (unlike defrag/balance/scrub) but I could set the schedule so that it runs instantly. And get that 526 up into production already as this forum is depending on you! You're like a one man team on here and for the most part one of the few that reliably responds to my post regardless of which section I post in. :smileylol:
We link enabling/disabling bit-rot protection to enabling/disabling CoW. The GUI option is set at the share level. So one share could have bit-rot protection enabled and another have it disabled.
Defragmentation breaks the CoW link between current data and snapshots, but it doesn't uncow a file.CoW should not be used where there are a huge number of modifications made in place to files.
mdgm wrote:We link enabling/disabling bit-rot protection to enabling/disabling CoW. The GUI option is set at the share level. So one share could have bit-rot protection enabled and another have it disabled.
Defragmentation breaks the CoW link between current data and snapshots, but it doesn't uncow a file.CoW should not be used where there are a huge number of modifications made in place to files.
Ok, the only share where there is a number of modifications going on is the backup share for my PCs and other files. The rest would be photos/vidoes/etc which sounds like may benefit from Bit-rot.
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