On Wed, 12 Jan 2005 07:25:43 +1100, Pete de Zwart <dezwart@froob.net> wrote:
[snip]
> improvement on I/O compared to the improvement potential of moving to
> SCSI/FCAL, that and getting more memory.
>
I would like to ask the question that continues to loom large over all
DBAs. SCSI, FCAL and SATA, which works best.
Most FCAL loops have a speed limit of either 1Gbps or 2Gbps. This is
only 100MB/sec or 200MB/sec. U320 SCSI can handle 320MB/sec and the
AMCC (formerly 3Ware) SATA Raid cards show throughput over 400MB/sec
with good IOs/sec on PCI-X.
I am not prepared to stand by whilst someone makes a sideways claim
that SCSI or FCAL is implicitly going to give better performance than
anything else. It will depend on your data set, and how you configure
your drives, and how good your controller is. We have a Compaq Smart
Array controler with a 3 drive RAID 5 than can't break 10MB/sec write
on a Bonnie++ benchmark. This is virtualy the slowest system in our
datacenter, but has a modern controler and 10k disks, whilst our PATA
systems manage much better throughput. (Yes I know that MB/sec is not
the only speed measure, it also does badly on IO/sec).
Alex Turner
NetEconomist
