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

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:

quoted

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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