On Tue, 9 Nov 1999 21:14:58 +0100, "GDN" <gert.deneve_at_advalvas.be> wrote:
>If you have a lot of I/O, the SSA architecture can become a bottleneck. All
>the data from the SSA-disks have to come across the same wire. Also you
>don't have any caching.
If you're not doing the HACMP thing you can always get the
32MB fast-write card for the SSA controller.
The following assumes that you're not using RAID5... ...and
not using HACMP...
If you've got (say) 8 drives and one SSA card, subdivide the
loop into 2 4-drive loops, giving you the ability to address
4 drives simultaneously (the SSA controller attempts dual
access via the 2 legs of the loop). If you've REALLY got a
need for speed you can cheat- get a second SSA card and
build 4 loops of 2 drives, giving you 40MB access to each
drive at all times... (OK, so you spend more money, but,
hey, this is "take no prisoners time". You also waste half
of the slots in the 7133 box.)
There are also some IBM pubs that describe various ways to
place the drives for tuning- none of which I have seen, much
less read. (Is this an adequate disclaimer?)
When you get into something much bigger, well, things get more
sticky and you have to make some more compromises- though (8)
36GB drives in a 7133 cabinet accessed in 4 loops via two SSA
cards will feel pretty good.
--
John R. Campbell Speaker to Machines soup_at_jtan.com
- As a SysAdmin, yes, I CAN read your e-mail, but I DON'T get that bored!
Disclaimer: All opinions expressed are those of John Campbell alone and
do not reflect the opinions of his employer(s) or lackeys
thereof. Anyone who says differently is itching for a fight!
Received on Thu Nov 11 1999 - 08:50:46 CST
