Re: question: no-bitmap RAID1 with off-site drive

[starlight.2012q4@binnacle.cx]

Good point but not an issue here.

Have daily offsite cloud incremental backup
in the mix here (i.e. forth drive).

The array does nothing but receive
incremental Bacula archives once a day
in the early AM.  So there's no
moving target data loss potential.


At 09:56 AM 11/12/2012 -0800, Drew wrote:
>> The third drive will never be on site
>> (think about the risk), but that just
>> means that the array will grow from
>> 2->1 and then from 1->2 instead
>> of from 2->3 and 3->2.
>
>I'd argue your risk from a failing disk during
>resync is significantly greater then your risk
>of facility failure during the same window. Not
>sure what drives are pricing where you are but
>adding a forth into the rotation is cheap
>insurance. Two for the array, one syncing, one
>offsite.
>
>Some recent blogs (
>http://storagemojo.com/2010/02/27/does-raid-6-stops-working-in-2
>019/
>for example ) suggest that modern drives will
>encounter unrecoverable read errors approx every
>12TB read. That works out to approx every
>6-12 resyncs based on 1-2TB drives.
>
>
>-- 
>Drew
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