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Forum Discussion
Dahwich
Mar 11, 2017Aspirant
ReadyNAS 104 rediculously slow scrub
I have a ReadyNAS 104 FW 6.6.1. I have 4x 3TB drives in RAID 5 with about 6TB of data. I recently did a full reset and restored all my data. This is the first scrub after that. I started the scru...
Anonymous
Mar 11, 2017The RN104 as a lowend nas is just lacking enough resources to conduct bitrot protection. If you have enabled that you might want to consider to switch this to disabled. With bitrot protection status "disabled" scrubbing is meaningless to my understanding and you should stop conducting it. It is just putting lots of stress on the disks and you are not getting any benefit of it.
Defrag and balance are ok, though.
Netgear moderators please correct me, in case I'm wrong on this.
- StephenBMar 13, 2017Guru - Experienced User
Retired_Member wrote:
With bitrot protection status "disabled" scrubbing is meaningless to my understanding and you should stop conducting it.
Bitrot protection works with RAID scrubbing to recover files when there is silent corruption. But RAID scrubbing has value even if bitrot protection is off. So I think your recommendation is incorrect.
Dahwich: Do you have disk spindown enabled?
- DahwichMar 14, 2017Aspirant
No, I do not have disk spindown enabled. Today, things are finally progressing at a resonable rate. It is finally up to 63% and will hopefully be done some time tomorrow, but still, that will be about 10 days!
- mdgm-ntgrMar 14, 2017NETGEAR Employee Retired
Which services are you running?
Which apps do you have installed?
- AnonymousMar 14, 2017
Then be so kind to share the advantage(s) of doing scrub with bitrot protection off, please.
- StephenBMar 14, 2017Guru - Experienced User
Retired_Member wrote:
Then be so kind to share the advantage(s) of doing scrub with bitrot protection off, please.
You are going off topic, but I will answer anyway.
The scrub maintenance task includes both a btrfs scrub and a raid scrub. Note that the raid scrub is available on older OS 4.2.x readynas as it's own maintenance function (even though OS4.2 has no bitrot protection).
The btrfs scrub provides some verification of the file system integrity, even if there are no checksums. The raid scrub also verifies that all the parity blocks in the RAID system are consistent with the data blocks. If a bad disk block is encountered during either scrub, the block should be re-allocated and it's contents reconstucted from the remaining data+parity blocks. And of course, the SMART logs will track the reallocated and pending sectors that are uncovered.
There are some posts about scrubs not being useful with jbod volumes (and checksums turned off). But that's a different setup than what we have here. Even then, I suspect that scrubs in those cases might still have some diagnostic value.
mdgm wrote:
Which services are you running?
Which apps do you have installed?Dahwich - it would be good to follow up with mdgm-ntgr on this, as something does appear to be interfering with the normal scrub.
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