I last wrote about my VMware home lab back in September, so here is an update. What I have found is that while the HP XW8600 is nice to have all those SAS/SATA connections and the memory, the IO performance is lacking. I currently have 4 SATA drives plugged in to the LSI 1068 Raid card that is on the motherboard. There are 2 1TB drives in a Raid 1, and 2 500GB drives in a Raid 1. But ever since moving to it I have been having really slow IO. As an example last night I was working with a simple MySQL database, it has one table with 2 columns in it. I went to insert 17,000+ rows and it took almost 20 minutes to do it. (On a different server with just IDE drives, it was less than a minute or two do to it.)
So I have been searching most of the weekend to see what I could find, ans there is tidbits of information everywhere on the interwebs. So I thought I would write down what I found and put it in one place for others to find.
It seems that the single biggest problem is “write cache”. Since the LSI 1068 on board raid controller doesn’t have a battery, it has to wait for the disk to report back that the data has been successfully written to the disk. This is complicated by the fact that I have a raid 1 set up, so both disks have to report that it is written and then the controller report back to VMware ok. In other words, there is no “cache” on this controller so the speed is limited to about 20Mb/s.
So how can I fix this? Well since I want the redundancy on the disks, making them single disks, while making it faster would not provide me any security of my data. This could work for a couple of my VM’s that are “disposable” test vm’s. But for ones that I want to keep I would need to keep them on a RAID. So to fix it, I need to find a PCI-E controller that has a cache and battery on it.
So my hunt begins, I will update once I can find one that works well.