[plug] Raid 0 software? hardware?

[Cameron Patrick]

Adrian Woodley wrote:

> /dev/md1:
> Timing cached reads:   1600 MB in  2.00 seconds = 799.32 MB/sec
> Timing buffered disk reads:   94 MB in  3.04 seconds =  30.94 MB/sec

That's pretty disappointing, actually, I see better linear speeds than
that on my laptop, and around double that on a single 7200rpm drive.

With 4 drives on an Athlon XP you'd expect to be limited by the PCI
bus, so that'd get a theoretical rate of around 100MB/s on the RAID
device.  Getting less than half of that in practice isn't great.

Take a peek at the results on UCC's new file server:

        http://lists.ucc.gu.uwa.edu.au/pipermail/tech/2005-April/002785.html

It's a dual Opteron with 4 SATA drives and a PCI-X SATA controller, so
it isn't limited by the PCI bus any more.  It's running Linux software
RAID 5 and gets around 173 MB/s read and 74 MB/s write, _through the
filesystem_.  Given that each of the drives can do 60MB/s, that's
within 5% of the theoretical performance (i.e. 3*60 or 180MB/s).  Not
bad going.

Cheers,

Cameron.