On Tue, 28 Jul 2009, Marc Cousin wrote:

> At peak during the night, we have around 40-50 write streams at the same time,
> and we are despooling to 3 LTO3 and 3 LTO1.

That's larger than my installation and I haven't got budget for a
dedicated array controller. We're using software striping on our disks.

> I think the most important is : don't purchase anything without doing
> benchmarks first for this special type of activity. That's what we did : we
> wrote a small program to simulate the expected throughput on the array with
> several streams, and only bought the array when we were satisfied with its
> performance, which required a bit of tuning (choose the right filesystem, the
> right scheduler, tune read ahead...). And I think this time wasn't wasted at
> all...

You're right, it isn't.

The main criterion is keeping up with the tape drive(s). Right now we are,
but that will change with a new robot purchase and that's why I'm looking
ahead.

AB




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