Matched or unmatched drives for RAID arrays?
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.
The advantages of matched drives are more of a value-economic stance. The array is only going to be as fast as the slowest drive. Other factors are logical, not physical (misaligned stripe array).
Using matched drives is not important. Especially with "normal conditions"
Value-economic stance: unless you are using really high-end devices (let's say SSD) with low-end drives (old hard disk), you are not saving by using matched drives, at least not substantial amount. Taking 1TB drive with 32MB cache from two manufacturers tend to be about equally priced.
Failing: it's possible disks from same batch break down at the same time. Probability is higher, but not really high. For RAID0 it doesn't really matter, in that case it may be better to have identical drives - if one is going to fail, everything is gone anyway. This is important for larger arrays including multiple disks - if you have 16x 2TB in RAID5, rebuilding will take long time (probably days), and then it's catastrophe if another disk fails. With RAID1 this is not major problem.
Speed: no, normal RAID controller/software RAID can't use full performance from disks with different speeds. In RAID1/RAID0 everything is striped 50% on both disks (in RAID1 mirrored equally). 50% of reads and writes goes to each disk, not depending on disk speeds.