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My V-Series NAS is running ontap 7.3, and gets all its disk from a SAN. LUNs are provisioned to the Netapp, which puts them into a raid-0. The SAN itself, of course, uses RAID with scrubbing and prefailure analysis. Basically, we use the SAN to handle all the disk, and the NAS as a file front-end. There are no Netapp native disks- even the filer's root aggregate is on the SAN.

That said, right now the weekly scrubbing that Netapp does is on (default):

nas> options raid.scrub.enable
raid.scrub.enable            on

Since the SAN takes care of its own disks, and since these are all LUNs that would only ever all fail at the same time, can I safely disable scrubbing? Does it do something more than disk checks?

Basil
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1 Answers1

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I'm pretty sure that you're correct - what RAID scrubbing does is read back your stripes and recalculate your checksums, and in this way check for media errors.

So if your array is already handling it, then it's moot. Perhaps to the point where if the NetApp thinks it's got a RAID-0, I'm not sure if it actually can be doing anything - there's nothing there to verify.

Can't find any reference to turning it off in the V-series guide I've got though.

Sobrique
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  • Thanks- I don't know how to tell whether the filer is doing these, but I do see suspect spikes in disk IO this would be a convenient answer to. – Basil Aug 28 '14 at 10:44
  • I've had a certain amount of success in hand rolling a monitoring solution - in diag mode, you get a lot of performance counters to track. Graphing disk KB against NFS/CIFS iops for example - I get a large surge of disk read KB across all my filers a little after midnight on Sunday, but no corresponding surge in front end IO. – Sobrique Aug 28 '14 at 10:51
  • Right, so I have spikes in the back-end LUN IO that don't correlate with changes to the front end work, I am thinking it might be a scrub. – Basil Aug 29 '14 at 11:19
  • Most likely explanation. Alternatively it's the dedupe scanner kicking off, which I think shows similar. – Sobrique Aug 29 '14 at 11:23
  • We don't use dedupe. – Basil Aug 29 '14 at 12:21