I've been doing some performance tests on a few of my drives lately, trying to figure out which combination of drive/raid-level(or not) will give me the best performance (for Hyper-V incase anyone's curious).
However, I'm seeing some behaviour/results that seems quite odd to me.
I'm using standard Windows Software Raid (ie, not fake motherboard raid, and don't want to spend the few hundreds of dollars I'd need to in order to get a decent hardware raid controller) for these tests. I'm not at all concerned about backups or drive failure (Windows Home Server, FTW!), I'm focussing strictly on performance. These tests are being executed in Windows 7 Ultimate (My server will end up being Server 2k8R2).
I've got two Western Digital Black 640Gb drives (SATA300) which give the following results using Atto Disk Benchmark (I also get similar results with SQLIO):
Drive Read Write 640(#1) 120 115 640(#2) 125 110 Mirror (Raid-1)* 82 77 Striped(Raid-0) 162 145
The unexpected result is the drastically poor performance fo the mirrored drives. I was expecting reads to be slightly better than a single drive, not significantly worse..
I've run the tests a number of times (breaking and recreating the array and mixing up the mirror vs striped vs single drive tests) with comparable results.
For anyone using a similar software raid setup, do these numbers jive with what you're working with, or are they completely off base? (Because the certainly seem so to me…)
Best Answer
If you don't wait for the array to sync after creating the mirror, you will see results like this. The drives need to be in sync to have a real measure of performance taken, otherwise they will be doing a lot of background reads and writes.