Spread out to max storage upgrades

Ron Keiper of the Nielsen Company asked how to maximize storage performance in his upgrade to HP’s XP series of disk arrays, linked to an HP 3000. This kind of upgrade is common in a site which is either homesteading or buying more time during a migration project.

We are in the process of migrating our HVD10 storage to an XP256 via FW-SCSI and IO Expansion (1828A) cabinets. Our performance testing thus far shows a large increase in CPU pause and disk queuing on the XP256 system. Job run time is similar, within 5-10 minutes on a one-hour job. I have seen many reports about the XP being a great deal faster, but we are not seeing that and have concerns about moving forward with our storage migration. I am wondering if it is set up properly for best performance.

The XP is set up Raid 1, I believe, (OPEN-9 in DSTAT) and are set up as HPDARRAY in SYSGEN. Is that the correct sysgen ID for the XP? There are a similar number of drives/LUNs on both of our test volume sets. The HVD is setup as Mirror/iX.

Craig Lalley of Echo Tech responds:

The XP256 is a decent box, but only half the speed of the XP512. The LDEV assignment within the XP is very important when it comes to performance.  Did you spread your LDEVs across ACPs and raidgroups?

You didn’t mention how much Array Cache you have in the XP256. Keep in mind the XP storage array is cache centric, meaning everything goes through cache. With the XP256, I would max out the array cache.

Lalley, who specializes in this kind of configuration upgrade, adds 

Remember, always spread your IO...  across XP ports, XP cards, XP array groups, XP ACPs, host HBAs, Host System Bus Adapters and switch ports.