Between 200 - 400 reads per second. Too much?

[Jeff Almaguer]

I'm getting between 200 and 400 read I/Os per second on a large LUSE used by Exchange. These numbers seem very low to me. How much read I/O can the XP1204 handle before Exchange users start to see any slowdown?

specs:
The XP1024 has 12Gbs of cache and is connected by a 2Gb fibre switch. The LUSE is striped evenly across the tops of 5 RAID groups.

[Peter Mattei · Accepted solution]

First thing you have to know is that LUSE is not striping but concatenating.
This means that if you write sequentially you write to the first ldev then to the second and so on.
Thus the max performance you can expect depends on the number of ldevs (Array Groups) your Exchange is using.

Looking at a single Array Group this is what you can expect:
RAID5 (3&1) 615 IOPs read @19ms response time
RAID5 (3&1) 300 IOPs read @9ms response time

RAID5 (7&1) 1020 IOPs read @15ms response time
RAID5 (7&1) 640 IOPs read @9ms response time

Thus best with Windows is using RAID5 (7&1) e.g. Raid 5 over two Array Groups of 8 disks, or for write intensive applications RAID1 (4&4) e.g. RAID1 over two Array Groups of 8 disks.
Remember: On the XP1024 you need to have 2 ACPs for either RAID5 (7&1) ore RAID1 (4&4).

So if your reads are spread over all ldevs in your LUSE you can achieve much more than 200 - 400 read IOs.
Best to find out the performance behavior is the use of Performance Advisor XP.

I suggest you also have a look at this XP/Exchange whitepaper
ftp://ftp.compaq.com/pub/products/storageworks/whitepapers/5982-7883EN.pdf

Cheers
Peter

[Jeff Almaguer]

Thanks!