Slow RAID 5 configuration

LlamaWithARifle · 5 Jan 2011 at 23:48

I've set up RAID 5 on my computer using 3 2tb seagate ST32000542AS drives on an Abit IP35 pro motherboard.

I went into bios and switched RAID on and set up two RAID 5 partitions across all 3 drives each being 1.8tb each, I then used the mobos CD to copy the drivers onto a floppy drive.

I then installed Windows XP onto one of the drives using F6 to install the RAID drivers.

When I booted into XP I installed all Microsoft updates and then I copied all my back up files, this is when I found that the set-up is running very slow, I'm getting roughly 20mb/s when copying files whether it be via usb or on the same hard drive.

I've tried installing Intel Matrix Storage console and I enabled Volume Write-Back cache and this did increase my speed from 5mb/s to what it is now 20mb/s

Have I missed something while setting up RAID, I've noticed that there are two versions of the drivers Intel and Jmicron versions, I'm not entirely sure which I used it was whatever the motherboards CD copied to my floppy drive.

Help would be greatly appreciated

edit - I also get a message when booting up that AHCPI BIOS Not installed, but I've assumed that this is normal as Windows boots up normally

rpstewart · 6 Jan 2011 at 10:32

Those speeds are about right for motherboard based RAID5. The controller doesn't have any hardware support for the XOR parity calculations so they have to be done (usually inefficiently) by the CPU - hence the poor speed.

My usual recommendation is not to bother with RAID5 unless you've got a decent hardware controller card.

Wucked · 6 Jan 2011 at 10:37

Yes, pretty much what rpstewart said. If you want RAID for fault tolerance then get a separate card.

LlamaWithARifle · 6 Jan 2011 at 10:54

Isn't 20mb/s copying slower then if I didn't have RAID at all? On Windows 7 I normally get around 30-40mb/s?

How much would a decent but fairly cheap RAID controller cost me? And what kind of speeds would I be getting on one?

rpstewart · 6 Jan 2011 at 13:09

Unless you need the availability that RAID5 gives you I wouldn't bother. RAID0 or single disks plus a decent backup (which you'd need with RAID5 anyway) will give you better performance.

LlamaWithARifle · 6 Jan 2011 at 14:26

If I were to set up RAID 0 what would be the best way of doing it using 3 hard drives?

Should I set up 3 volumes across all 3 drives or set up 2 volumes on 2 drives and use the remaining hard drive as a backup device?

What kind of difference is there between RAID 0 split across more than two drives?

Edit - Well I set up RAID 0, making two volumes split across two of my hard drives leaving me with 2 1.8TB volumes and I plan on using my remaining drive as a backup.
So far performance is a little better, getting a constant 30mb/s copy speed but that's without Write Back Cache, I heard it is not a wise idea to enable it while using RAID 0, is this true or should I enable it?