Op 2013-03-27 om 13:12 schreef Paul Mather:
> On Mar 26, 2013, at 11:44 PM, Bill Arlofski wrote:
> > On 03/26/13 22:33, Wood Peter wrote:
> >> Hi,
> >>
> >> I'm planning to use Bacula to do file level backup of about 15 Linux
> >> systems. Total backup size is about 2TB.
> >>
> >> For Bacula server I'm thinking to buy Dell PE R520 with 24TB internal
> >> storage (8x 3TB disks) and use virtual tapes.
> >
> > Hi Peter. First, you're going to want some RAID level on that server and
> > RAID0 is not (IMHO) RAID at all. :)
> >
> > At a minimum you're going to want to set up (for example) RAID5 in the
> > server
> > which will give you a maximum of 7 x 3 = 21 TB since the equivalent of 1
> > full
> > drive is used for parity, spread across all of the drives in a RAID5 array.
> >
> > Having said that, RAID5 does not have the best write speeds, but other RAID
> > levels that will give more redundancy and better write speeds will use
> > significantly more drives and give you less total storage. You may need to
> > spend some time to consider your redundancy and read/write throughput
> > requirements.
> >
> > Also, you will generally want to configure at least one drive as a hot spare
> > so the RAID controller can automatically and immediately fail over to it in
> > the case of a drive failure in the array.
> >
> > So that takes away at least 3 more TB, so now your down to 18TB total
> > storage
> > with a minimally configured RAID5 array with 1 hot spare.
> >
> > Just some things to consider. :)
>
>
> Another thing to consider is that with large capacity drives (3 TB)
> combined into large RAID-5 arrays there is an increased likelihood of
> a catastrophic array failure during an array rebuild due to an initial
> drive failure. For this reason, RAID-6 would be preferred for such
> large arrays.
>
> Reliability of large RAID arrays is one of the motivations
> behind raidz3 (triple-parity redundancy) in ZFS. See, e.g.,
> http://queue.acm.org/detail.cfm?id=1670144 for details.
>
Thanks for the advice on RAID configuration. Now we can go back to
> >> 24TB internal storage (8x 3TB disks) and use virtual tapes.
so (cheap) disks as alternative to backup tapes.
Groeten Stappers
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