64-bit OS affects SSD raid performance

Hello,

I recently bought four SSD drives and hooked them up in RAID 0 configuration with an Adaptec card. I was hoping to leverage my full 4GB of RAM by using Windows 7, but was disappointed to find out that while sequential write didn't differ much, sequential read performance I benchmarked (~410 mb/s) was less than half than on 32-bit Windows XP Pro SP3 (~830 mb/s). Thinking it was a Windows 7 issue, at first I tried the latest drivers, and after that Windows XP Pro 64-bit edition. However, the same poor performance remained, even with upgrading the intel SSD to the improved 8820 firmware. Listed below are the details of my hard and bench. Has anyone else had similiar problems? Why would using a 64-bit OS be an issue in hard disk performance?

Thank you for the help!

ssd: intel X25-M Mainstream SATA SSD SSDSA2MH080G1 x 4 drives
raid card: adaptec raid 5405
M/B: asus P5Q PRO

--------------------------------------------------
CrystalDiskMark 2.2 (C) 2007-2008 hiyohiyo
Crystal Dew World : http://crystalmark.info/
--------------------------------------------------
Sequential Read : 410.134 MB/s
Sequential Write : 177.697 MB/s
Random Read 512KB : 339.542 MB/s
Random Write 512KB : 130.702 MB/s
Random Read 4KB : 13.992 MB/s
Random Write 4KB : 20.905 MB/s
Test Size : 100 MB

It's mostly likely a driver issue with your Adaptec card. Contact them.

Windows 7 is still not RTM yet so don't expect full support.

Your probably getting about 3GB give or take depending on setup (mainly graphics). There's very little difference between having 3GB and 4GB. There is no game that will run any differently between 3GB and 4GB.

Vista and Windows 7 don't impress me that much. Vista not at all, Windows 7 did but several tiny issues ruined the experience for me. Maybe later.

Anyway, there may be some other issue affecting your speed so I'd contact your SSD manufacturer as well.

Could you test with ATTO please, and show me both the score you get on Win7 (poor) and on XP (good). This could just be the result of improper benchmarking, and i don't know CrystalMark.

I would still like to see the ATTO screenshot, if you can post one. ATTO can be found with google, doesn't require installation just a single .exe.