What CPU's do you have in your 2950? I'm backing up to two LTO-2 in my
PowerEdge 2900 server (dual Xeon 5160 CPU's) and it seems to be pretty
maxed out with two tape drives. On my R710 I only get 70MB/sec despool
rates to LTO-4 drives.
If you can't get higher results when using a SAN I'd think that the
bottleneck is the server CPU. If you're not CPU bound, then increasing the
read cache wherever you're holding the spool should help.
Bob
> From: Athanasios Douitsis <aduit...@noc.ntua.gr>
>
> Hi everyone,
>
> Our setup consists of a Dell 2950 server (PERC6i) w/ FreeBSD7 and two HP
> Ultrium LTO4 drives installed in a twin Quantum autochanger enclosure.
> Our bacula version is 5.0.0 (which is the current FreeBSD port version).
>
> Here is our problem:
>
> When running a single job, our setup is able to consistently surpass
> 70Mbytes/sec (or even 80) on despooling, which should be reasonably
> enough. Unfortunately, when running several jobs on both drives (for
> example 6+6 parallel jobs) our despooling speeds drop to about
> 20Mbytes/sec or even less. The speed of the jobs to finish last
> naturally ramp up, especially for the very last. Our hypothesis is that
> the spooling area cannot handle simultaneous reading (from jobs that are
> still tranfering) and writing (from the currently despooling job) too
> well, hence the performance loss.
>
> So far we were using a common spool area for both drives on these two
> test setups:
>
> 1)A spool area on a Clarion CX4 Fibre Channel array (4Gbps) w/ 2x10Krpm
> disks on a raid0 configuration.
> 2)A 2xSCSI320 raid0 striped configuration in the server itself (via the
> PERC6i controller).
>
> Both setups yielded similarly poor results.
>
> Our thoughts/questions:
>
> -Should we use a separate spool area for each drive?
> -Anyone else that has had problems with the despooling speed being too
> low? What are your proposed solutions, if any?
>
> I realize this is not strictly a bacula question, however the matter
> should be of interest for any bacula admin out there. I understand that
> under like 40Mbytes/sec the drive constantly starts and stops, a
> process which is detrimental to its expected lifetime (and the tape's
> as well).
>
>
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