Looking around there is conflicting information on this, with some strongly suggesting one or the other.
From my understanding the issue with matched drives is that the wear on both drives is more or less the same, so the potential for the second drive failing with or very soon after the first is pretty high.
People also claim matched drives give substantially higher performance however assuming the unmatched drives are more or less the same (e.g. 2, 1 TB SATA II 7200rpm drives with 32MB cache), would the minor differences between say a Seagate and a Western Digital one (say one has a 128MB/s read rate, and the other a 150MB/s read rate, as well as I guess various other minor differences) actually cause any notable performance loss, i.e. potentially worse than two matched 128MB/s drives, or does RAID not really care and give you essentially an optimal solution (e.g. up to 278MB/s total read speed for RAID 0 and 1) and similar for other RAID with more "unmatched" drives (5 and 1+0 come to mind as possibilities)?
Also I couldn't find much info on how this is different on different RAID setups, e.g. RAID 0 or RAID 1, software or hardware RAID, etc. I'm assuming such things have an effect, and that's it's not all the same for RAID in general?
Best Answer
Points to remember for a RAID 1:
The SLOWER of the drives... will dictate the overall speed.
The SMALLER of the drives... will dictate the overall size.
If you are ok with that.... it's far better TO have drive as different as possible. Purchased at different times, from different stores, made by different manufacturers.
Reason? When the drives fail... I WANT them to fail at different times... not at the same time.