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Re: suggestion for a disk-to-disk backup server
2007-06-25 10:34:06
In addition to doing everything to make sure a backup disk failure
does not destroy all your backups you need to take into consideration
the length of your cycle.
My experience so far has been with tape and I am just beginning in the
disk-to-disk with virtual tape. How long before Amanda can reuse one
of your virtual tapes? The initial backup is going to be all level 0.
After that the planner is going to try for a balanced mix of fulls and
incrementals. The size of the incrementals depends on the amount of
activity on a filesystem. Some will change a lot; some won't change. I
would count on 30% of your backup size being backed up every day. For
disk-to-disk your backup server is definitely going to contain
multiples of your full backup size rather than a fraction of your full
backup size.
Can we get to the point of making a formula? I'll go out on a limb and
put some figures down. So much of it depends on amount of compression,
activity of users, and growth:
(days per cycle) * (size of full backup) * (average daily fraction of full)
let's say your 2 TB compresses to 1.5TB:
30 days * 1.5 TB * 1/3 = 15 TB for a full cycle.
If you've been backing up the same servers to tape already you can
plug in more accurate numbers for your site.
Quoting Matt Hyclak <hyclak AT math.ohiou DOT edu>:
On Sun, Jun 24, 2007 at 11:43:26PM -0700, Rudy Setiawan enlightened us:
I am trying to create backup servers out of the following specs:
P4 3.0Ghz
1GB RAM
RAID0 - 750GB x 2 (SATA)
Hosts to backup: about 20 hosts with roughly 100GB each host.
What will be the complications and the limitations?
And also what are the recommendations?
You realize that by using RAID 0, you are doubling the chance of losing all
of your backups, because there is NO redundancy - so if either of your disks
has a problem, you lose the entire array. If it is only temporary and you
are then moving the data to something else, that might be all right, but I
wouldn't feel comfortable with my backups (or anything other than scratch
space, really) being on RAID 0. I would use RAID 1, or if you have disks to
spare RAID 10.
Matt
--
Matt Hyclak
Department of Mathematics
Department of Social Work
Ohio University
(740) 593-1263
Charlie Reitsma
x6642
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