How similar do HDD's need to be for RAID setup?

[Stephince]

I currently have 2 http://www.ilgs.co.uk/products.asp?partno=ST3320620AS and although i could buy another through them i have never head of them. I could however buy a http://www.ilgs.co.uk/pp/data_storag...ard_Drive.html from Scan/Novatech etc.

They are about as similar as they can possibly be. Are they close enough/does it matter etc?

[peterb]

Ideally they need to be similar. If they are of different sizes in RAID 1 the size will be limited to the smallest. In RAID 0 you will get twice the size of the smallest. Read write speed will be limited to that of the slowest.

[arthurleung]

Depends on if you're expanding a RAID or creating a new RAID array.

If you're expanding RAID1 / migrating to RAID5, your new drive must be at least the same size as the other HDDs (perhaps +- 100M).

If it is a new array you're planning, then size doesn't matter. The smallest drive in the array decide the total size.

In terms of performance, if you buy ONE of the newest drives like Spinpoint F2, you will get better performance then the two 320GB you have at the moment. (These drives with 500GB platters are literally twice as fast). And you can sell the two smaller drives to recoup the extra cost.