vinum performance

[Greg 'groggy' Lehey]

On Sunday, 30 March 2003 at 13:00:56 +0200, Lukas Ertl wrote:
> Hi,
>
> I currently have access to a bunch of disks and a fat machine so I took
> the chance and performed some vinum benchmarks. You can find the results
> at <http://mailbox.univie.ac.at/~le/bonnie.html>.
>
> I created several RAID 0 and RAID 5 volumes with different stripe sizes
> and let bonnie++ run over the filesystems.

As I keep saying, bonnie measures systems, not storage.  Hint: ignore
any test which uses over 10% CPU time.  That leaves you with random
seeks.

> I was quite disappointed about the RAID 5 performance, and even the
> RAID 0 performance wasn't too good (a plain single disk filesystem
> was almost as fast as or even faster than a RAID 0 stripe, and I
> wouldn't expect that).

I would.  You're measuring the system, not the subsystem.

> RAID 5 performance was really a mess, some of the test took more
> than 30min. to complete.

It's interesting to note that some of the "CPU intensive" tests did
very little with RAID-5.  It would be interesting to find why, though
the problem could be with the benchmark.  To find out what's going on,
you'd need:

1.  Understand what bonnie++ is doing for these tests.  I've measured
    with bonnie, and in the process discovered that only the random
    seeks test comes close to measuring the disk, but the sequential
    I/O looked nothing like that.

2.  Use Vinum's built-in monitoring capabilities to see what's really
    getting as far as Vinum.  Look at the info command.

Apart from that, it would be interesting to see what rawio shows.
That, at least, goes to the disk.

Greg
--
See complete headers for address and phone numbers
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 187 bytes
Desc: not available
Url : http://lists.freebsd.org/pipermail/freebsd-stable/attachments/20030331/175fc737/attachment.bin