On Mon, 24 Apr 2006, Mark Kirkwood wrote:
> If I'm reading the original post correctly, the biggest issue is likely
> to be that the 14 disks on each 2Gbit fibre channel will be throttled to
> 200Mb/s by the channel , when in fact you could expect (in RAID 10
> arrangement) to get about 7 * 70 Mb/s = 490 Mb/s.
The two controllers and two FC switches/hubs are intended for redundancy,
rather than performance, so there's only one 2Gbit channel. I don't know
if its possible to use both in parallel to get better performance.
I believe it's possible to join two or more FC ports on the switch
together, but as there's only port going to the controller internally this
presumably wouldn't help.
There are two SCSI U320 buses, with seven bays on each. I don't know what
the overhead of SCSI is, but you're obviously not going to get 490MB/s
for each set of seven even if the FC could do it.
Of course your database may not spend all day doing sequential scans one
at a time over 14 disks, so it doesn't necessarily matter...
