Scenario: we're running a large (3TB total in cluster) Solr installation in EC2. I'm only concerned about disk performance on the read side of things. We suspect that we are limited by disk I/O and specifically get problems when an EBS volume decides to get flaky and slow down.
I am considering trying out RAID 1. From what I understand Linux software RAID will split the reads between disks, but I'm not sure how smart it is. If one of the disks in a RAID 1 pair gets backed up on reads, will it send more reads to the other disk? If a read has been pending too long, will it reschedule that read to the other disk?
I can't think of any way to test this behavior. I'd be happy to look through the code, but I'm not even sure if this would be handled by the I/O scheduler or if it's part of the raid drivers. I can't find any documentation that goes into any more depth than the software RAID HowTo.