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Re: [Amanda-users] Advice needed on Linux backup strategy to LTO-4 tape
2009-08-14 17:24:55
Rory Campbell-Lange wrote:
Hi Chris
On 13/08/09, Chris Hoogendyk (hoogendyk AT bio.umass DOT edu) wrote:
<snip>
Typically, we set up Amanda with holding disk space.
<snip>
If all the storage is locally attached (actually, AoE drives storage
units connected over Ethernet), I am hoping to avoid the disk space if I
can write to tape fast enough. I'd like to avoid paying for up to 15TB
of fast holding disk space if I can avoid it.
So, one way would be to logically divide the storage into smaller DLE's.
A DLE (Disk List Entry -- http://wiki.zmanda.com/man/disklist.5.html)
for Amanda can be a mount point or directory. Obviously, I don't know
how your storage is organized; but, if you can define your DLE's as
separate directories on the storage device, each one of which is much
smaller, then you could use a smaller holding disk and still benefit
from Amanda's parallelism. In one of the other departments here, the
sysadmin has successfully divided a large array this way and is driving
LTO4 near top speed.
Compression can be done either on the client, on the server, or on
the tape drive. Obviously, if you use software compression, you want
to turn off the tape drive compression. I use server side
compression, because I have a dedicated Amanda server that can
handle it. By not using the tape drive compression, Amanda has more
complete information on data size and tape usage for its planning.
If your server is more constrained than your clients, you could use
client compression. This is specified in your dumptypes in your
amanda.conf.
I don't have any clients, so this is an interesting observation. I'll be
trying to do sofware compression then I think. The Unix backup book
(google for "amanda software compression") suggests that compression can
be used on a "per-image basis"; presumably I can pass the backup data
stream through gzip or bzip2 on the way to a tape?
Amanda will do the compression for you. You define it in the dumptype in
amanda.conf. If you have a holding disk, then it will compress the data
as it goes onto the holding disk. If you don't have a holding disk, then
you might have issues with being able to stream a backup to tape,
compressing it on the fly. Even with a really fast cpu, I don't know if
you can maintain the throughput to drive LTO4 at a good speed.
--
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Chris Hoogendyk
-
O__ ---- Systems Administrator
c/ /'_ --- Biology & Geology Departments
(*) \(*) -- 140 Morrill Science Center
~~~~~~~~~~ - University of Massachusetts, Amherst
<hoogendyk AT bio.umass DOT edu>
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Erdös 4
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