[ale] raid suggestions

[Lightner, Jeff]

If it takes 36 hours to restore how are you backing it up in the first place?

RAID != substitute for backups.

RAID is intended to help preserve uptime because restore is always a PITA due to downtime but it can not be relied upon to prevent all failures.   What happens if the cabinet the disks are in catches fire?

We certainly do a lot of RAID storage both internal to servers with controllers and external via disk arrays on fibre SANs but we ALSO do backups AND send data offsite in case our data center gets destroyed.





-----Original Message-----
From: ale-bounces at ale.org [mailto:ale-bounces at ale.org] On Behalf Of mike at trausch.us
Sent: Friday, February 10, 2012 11:10 AM
To: ale at ale.org
Subject: Re: [ale] raid suggestions

On 02/10/2012 04:44 AM, Jim Lynch wrote:
> Has the concern about the possibility of the hardware controller
> breaking and being out of production been eliminated?  At one time I
> recall the suggestion that using hardware raid was a bad idea because if
> the controller went OTL and there wasn't another available you'd get to
> start from scratch.  I believe this concern was with the controllers on
> the MB however.
>
> That of course can be alleviated by proper backups.  I always thought
> that was somewhat meaningless in a lot of cases 'cause I'd think many
> raid installations were to support a backup set of drives.  Not all, of
> course, but surely that's a common purpose for a raid set.

I don't know about many other RAID deployments, but the one that I spend
the most time interacting with would take about 36 hours to restore from
backups, given the amount of data sitting on it and the lack of a huge
tape drive to store backups on.  I seriously do not like that idea,
which is why I try to proactively ensure that all the disks in the array
are in good health.  It takes only about 18 hours to rebuild a disk in
the array, but it takes double that to restore... and for that matter,
rebuilding a disk in the array can happen while the array is in use,
while restoration would mean that the business would be down for the
duration.  That's kind of annoying.

For that reason, I'm trying to get some sort of second RAID there and
see about running something like DRBD running on both RAID arrays, that
way if one array goes down completely the other one will keep running
until the failed one is repaired.

        --- Mike

--
A man who reasons deliberately, manages it better after studying Logic
than he could before, if he is sincere about it and has common sense.
                                   --- Carveth Read, "Logic"





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