[clug] Is a weekly RAID scrub too much?

Paul Wayper paulway at mabula.net
Sun Feb 26 06:15:54 UTC 2017

On 24/02/17 22:35, Eyal Lebedinsky wrote:
> I was idly browsing when I came upon an announcement from Toshiba of a new NAS
> HDD family:
>     https://toshiba.semicon-storage.com/ap-en/product/storage-products/client-hdd/mn05aca-mn04acaxxx.html
> I took a look at the spec
>     https://toshiba.semicon-storage.com/content/dam/toshiba-ss/asia-pacific/docs/product/storage/product-manual/cHDD-MN05ACA_MN04ACA_Product-overview.pdf
> and there I see
>     "Rated Annual Workload (Total TB Transferred per Year, R/W)   180 TB/year".
> and this is the same for the three models 4/6/8TB.
> Doing the math: a weekly scrub will read 52*8=416TB a year, more than twice
> the designed load.
> Even a monthly scrub will use up more than half the workload.
> Is the scrub doing more harm than good by shortening the service life of the
> disk?

So, what do you mean by "weekly RAID scrub"?

I've never heard of anyone doing this on a RAID array.

I've used 'scrub' on a disk or files to overwrite them with random data to
avoid anyone using a scanning electron microscope on them to view your data
again.  With disk geometries, cylinder tolerances, and encoding mechanisms
these days, even overwriting with zeros will render the data inaccessible to
almost all attackers.

But I've never heard of 'RAID scrubbing'.  What are you doing, Eyal?

Have fun,


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