[mythtv-users] Raid Performance Tweaking

[Blammo]

On 7/8/06, Jens Axboe <mythtv-users at kernel.dk> wrote:
> On Fri, Jul 07 2006, Blammo wrote:
> > While your average current disk drive, on sustained SINGLE threaded
> > reads, sits about 40MB a second, flipping to reads/writes, or 2/3/4
> > simult reads/writes from different parts of the disk, and now your
> > throughput on that single spindle is going to be WAY down below that
> > magical 40MB number, and you will start having performance issues.
>
> That's only really true for the 'classic' io schedulers that are work
> conserving. At least on Linux, using 'cfq' or 'as' easily do a lot
> better for many reading clients (or mixed read/write workload) at the
> cost of slightly higher latency.

Agreed, that can help a whole bunch. I'm a big fan of "deadline"
myself for my backends.

However, scheduler or no, random read/write speeds are always lower
than sequential, which is a close comparison to an example of 3
clients reading/writing to the disk at the same time, plus local
activity.