Data check/scrub RAID 1 - how often?
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How often does it makes sense to do a data scrub on an md software RAID 1 array?
The system I'm looking at have a 2x4TB array and runs the data scrub once per week (CentOS). It feels like it's way too often but I'm not sure.
According to the logs it takes about 7.5 hours to complete so it's basically running at full speed (avg 155MB/s). Probably because it's running on weekends. It will likely take twice as long when there is more disc activity.
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@Pete-S said in Data check/scrub RAID 1 - how often?:
It feels like it's way too often but I'm not sure.
Too often? I'd lean to too infrequent. Why not scrub daily? I believe that most people consider daily to be the "baseline."
Most enterprise RAID systems scrub constantly.
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@scottalanmiller said in Data check/scrub RAID 1 - how often?:
@Pete-S said in Data check/scrub RAID 1 - how often?:
It feels like it's way too often but I'm not sure.
Too often? I'd lean to too infrequent. Why not scrub daily? I believe that most people consider daily to be the "baseline."
Most enterprise RAID systems scrub constantly.
Maybe you're right. We have a few other RAID 6 arrays that are in the +30TB range and they are scrubbed monthly.
Scrubbing is mostly a sequential read of all sectors so I guess it's about the same wear on the disks if they are scrubbing or if they just are spinning doing nothing.
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@Pete-S said in Data check/scrub RAID 1 - how often?:
Scrubbing is mostly a sequential read of all sectors so I guess it's about the same wear on the disks if they are scrubbing or if they just are spinning doing nothing.
Pretty much, yeah. If you can run it as a continuous background process, that's roughly ideal.
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@Pete-S
Monthly or twice a month at night, Scrubbing will check each block and that takes alot of time and performance.
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Obviously one of you are wrong.
So proof time. Backup your statements.
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@JaredBusch said in Data check/scrub RAID 1 - how often?:
Obviously one of you are wrong.
So proof time. Backup your statements.
All enterprise systems that are preconfigured do it either continuously or daily. Unfortunately, scrubbing isn't all that important (contrary to what people want to tell you about it being magic) and so even doing it never works out just fine for essentially everyone.
That scrubbing is a big deal at all is one of those ZFS myths that has crept into other areas. It is good, but most people learned about it from ZFS, thought it was magic, demanded to use it, blah blah.
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This write up sums it up well. It's a "it depends." It depends because it impacts you potentially and generally isn't very important. So therefore, there is no hard and fast guideline.
https://serverfault.com/questions/588217/how-often-should-i-scrub-my-raid
