Poor Performance with HP E200i RAID Controller and Solution

I thought I would share my experience here as it may be relevant to others using DSS.

The short answer = ENABLE the write cache BUT set the WRITE CACHE to 0% via the HP CLI. [ctrl slot=0 modify cacheratio=100/0 | ctrl slot=0 modify dwc=enable] Turn it on, but don't use it, go figure!

I just set up an Open-e DSS V6 server on an HP ML350 G5 with a E200i RAID controller, 128MB BBWC, and 6 x 1.5 TB 7200 RPM drives in a RAID 10 array. I was getting very bad performance, less than 100 iostats on an iSCSI file I/O volume high initialize rate. I have similar configurations using 3Ware 9550 cards producing well over 1000 iostats so I was trying to figure out what the ??? was going wrong.

A bit of research directed me to an Experts-Exchange article (http://www.experts-exchange.com/Stor..._24947953.html) and a few other sites. It would appear the RAID 5 processor and write cache are troublesome components to this controller. I wasn't using RAID 5 so I experimented with the read/write cache through the HP controller CLI that Open-e conveniently puts in their software.

The CLI was running VERY SLOW, commands took a minute to respond. Finally the above command made the array perform closer to expectation. I am now seeing almost 1000 iostats and the CLI is responding normally. Yes, you have to enable the write cache and set it to 0%. No other combination seems to work. Even using the disable write cache option failed to provide acceptable performance.

Tim