ReadyNAS 104 rediculously slow scrub

Question

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.&nbsp;I started the scrub over 8 days ago and it is only at 15.5%!!! It is not dead, it is very slowly progressing. Luckily, the NAS is functional during this but this is rediculous. I have checksums on, no virus scanner, and the only thing running is stock DLNA.&nbsp;The top command shows:&nbsp; PID USER&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; PR&nbsp; NI&nbsp;&nbsp;&nbsp; VIRT&nbsp;&nbsp;&nbsp; RES&nbsp;&nbsp;&nbsp; SHR S %CPU %MEM&nbsp;&nbsp;&nbsp;&nbsp; TIME+ COMMAND15673 root&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 20&nbsp;&nbsp; 0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0 R 28.8&nbsp; 0.0&nbsp; 89:22.51 kworker/u2:123180 root&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 20&nbsp;&nbsp; 0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0 R 28.8&nbsp; 0.0&nbsp; 26:03.81 kworker/u2:526359 root&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 20&nbsp;&nbsp; 0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0 R 28.1&nbsp; 0.0&nbsp;&nbsp; 1:54.39 kworker/u2:7&nbsp;1042 root&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 20&nbsp;&nbsp; 0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0 S&nbsp; 3.2&nbsp; 0.0 472:55.50 md127_raid5&nbsp;2403 root&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 19&nbsp; -1&nbsp; 218312&nbsp; 37916&nbsp;&nbsp; 8984 S&nbsp; 1.6&nbsp; 7.5 174:43.55 readynasd&nbsp;6093 root&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 19&nbsp; -1&nbsp;&nbsp; 19736&nbsp;&nbsp; 1368&nbsp;&nbsp; 1200 S&nbsp; 1.6&nbsp; 0.3 228:23.57 btrfs&nbsp; 972 root&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0 -20&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0 S&nbsp; 1.0&nbsp; 0.0 107:51.50 kworker/0:1H&nbsp;2893 root&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 20&nbsp;&nbsp; 0&nbsp;&nbsp; 16736&nbsp;&nbsp; 6352&nbsp;&nbsp; 3484 S&nbsp; 0.6&nbsp; 1.2&nbsp;&nbsp; 0:10.47 apache2&nbsp;4773 admin&nbsp;&nbsp;&nbsp;&nbsp; 20&nbsp;&nbsp; 0&nbsp;&nbsp; 17044&nbsp;&nbsp; 7236&nbsp;&nbsp; 4148 S&nbsp; 0.6&nbsp; 1.4&nbsp;&nbsp; 0:00.62 apache225892 root&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 20&nbsp;&nbsp; 0&nbsp;&nbsp;&nbsp; 5680&nbsp;&nbsp; 2568&nbsp;&nbsp; 2136 R&nbsp; 0.6&nbsp; 0.5&nbsp;&nbsp; 0:06.95 top&nbsp;2257 root&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 20&nbsp;&nbsp; 0&nbsp;&nbsp;&nbsp; 1888&nbsp;&nbsp; 1360&nbsp;&nbsp; 1264 S&nbsp; 0.3&nbsp; 0.3&nbsp;&nbsp; 0:06.78 wsdd2&nbsp;2891 root&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 20&nbsp;&nbsp; 0&nbsp;&nbsp;&nbsp; 1752&nbsp;&nbsp; 1220&nbsp;&nbsp; 1148 S&nbsp; 0.3&nbsp; 0.2&nbsp;&nbsp; 0:00.09 apache_log&nbsp;6090 root&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 39&nbsp; 19&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0 R&nbsp; 0.3&nbsp; 0.0&nbsp; 66:21.05 md127_resync&nbsp;Any ideas why this is so bad? In the past scrubs have taken 3-6 days which is also horrible but this is much worse.&nbsp;

StephenB · Answer

Retired_Member wrote:
StephenB
&nbsp;
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.
&nbsp;
The scrub maintenance task includes both a btrfs scrub and a raid scrub. &nbsp;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).
&nbsp;
The btrfs scrub provides some&nbsp;verification of the file system integrity, even if there are no checksums. &nbsp;The raid scrub also verifies that all the parity blocks in the RAID system are consistent with the data blocks. &nbsp;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. &nbsp;And of course, the SMART logs will track the reallocated and pending sectors that are uncovered.
&nbsp;
There are some posts about scrubs not being useful with jbod volumes (and checksums turned off). &nbsp;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&nbsp;- it would be good to follow up with&nbsp;mdgm-ntgr&nbsp;on this, as something does appear to be interfering with the normal scrub.
&nbsp;

Retired_Member · Answer

The 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.

StephenB · Answer

Retired_Member wrote:
With bitrot protection status "disabled" scrubbing is meaningless to my understanding and you should stop conducting it.

&nbsp;Bitrot protection works with RAID scrubbing to recover files when there is silent corruption. &nbsp;But RAID scrubbing has value even if bitrot protection is off. &nbsp;So I think your recommendation is incorrect.
&nbsp;
Dahwich: Do you have disk spindown enabled?
&nbsp;
&nbsp;

Dahwich · Answer

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-ntgr · Answer

Which services are you running?Which apps do you have installed?

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ReadyNAS 104 rediculously slow scrub

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