Scrub [skruhb]
verb (used with object), scrubbed, scrubbing.
to rub hard with a brush, cloth, etc., or against a rough surface in washing.
to subject to friction; rub.
to remove (dirt, grime, etc.) from something by hard rubbing while washing.
(Dictionary, 2015)
In IT Scrub Usually Equals Destroy
If you've got a similar background in computers to me “scrubbing” was something you did to an HDD to ensure there was no usable data on it before you environmentally responsibly disposed of it at a recycling depot. A “scrubbed” HDD could only be made better and safer if you smashed it with a hammer. No platters, no data, no problem.
So I completely understand why you would baulk at the idea of using any kind of scrub command on your production SAN.
NetAPP Scrub Increases CIA
Despite the terrible name if your SAN is running NetApp’s Data ONTAP a “scrub” is exactly what you want to do as it increases data availability by checking your disks for errors and inconsistencies and then if necessary using the parity disks to re-create the data and re-write it back to the RAID group (NetApp, 2013). By running scrub you increase the consistency, integrity and availability (CIA) of your data.
In short: in NetApp land a “scrub” is a very good thing as it protects the integrity of your data.
By default Data ONTAP performs weekly scrubs starting at 1:00am on Sunday mornings so you may not even be aware this feature is running. The process consumes very little in the way of system resources and is throttled back if user activity is detected but should the default schedule not suit your organisation you can alter it with the OPTIONS RAID.SCRUB.SCHEDULE command. You may want to consider the SYSSTAT command to confirm scrub is not consuming resources or find a convenient time to reschedule scrub.
Scrubs can be manually run but will fail on any degraded RAID group. If you've got a degraded group chances are you’re completely occupied just waiting for the NetApp tech to turn up and replace the disk (this happens automatically as well as Data ONTAP contacts NetApp directly when a disk RAID group fails without stopping to get your approval first).
You can run a scrub on a double-parity RAID group if one disk has failed but again – you’ve probably got better things to think about at that stage.
Conclusion
Scrub is a feature Data ONTAP uses to automatically verify your data integrity and increase data consistency, integrity and availability. It is enabled on your NetApp SAN by default and despite its terrible name it is a very good thing.
References
Dictionary (2015). Scrub. [ONLINE] Available at: http://dictionary.reference.com/browse/scrub. [Accessed 22 March 15].
NetApp (2013). How RAID-level disk scrubs verify data integrity. [ONLINE] Available at:https://library.netapp.com/ecmdocs/ECMP1196912/html/GUID-81F8BEA3-ADC1-4790-81F1-3E376BC98B27.html. [Accessed 22 March 15].
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