Nice, I thought RAID 1 just gave redundancy.

I use mdadm's RAID 10 on 2 drives for redundancy and speed.

"In mdadm, the RAID10 level creates a single complex software RAID that combines features of both RAID 0 (striping) and RAID 1 (mirroring). Multiple copies of all data blocks are arranged on multiple drives following a striping discipline." http://doc.opensuse.org/products/draft/SLES/SLES-storage_sd_...

RAID 1 mostly gives more random read IOPS, not faster. You have two drives from which to read data, since they're mirrored.

You do have more chances for the spindles to be near your data (especially with >2 drives in the array), which can slightly reduce average latency, but that isn't as large an effect.

I'd use the term "can" rather than "does" just because the performance is tiny[0] and some RAID controllers don't do a very good job utilising it.

[0]http://kmwoley.com/blog/?p=429