Sybase Question:

RAID
RAID means several things at once. It provides increased performance through disk striping, and/or resistance to hardware failure through either mirroring (fast) or parity (slower but cheaper).

RAID 0
RAID 0 is just striping. It allows you to read and write quickly, but provides no protection against failure.

RAID 1
RAID 1 is just mirroring. It protects you against failure, and generally reads and writes as fast as a normal disk. It uses twice as many disks as normal (and sends twice as much data across your SCSI bus, but most machines have plenty of extra capacity on their SCSI busses.)
Sybase mirroring always reads from the primary copy, so it does not increase read performance.

RAID 0+1
RAID 0+1 (also called RAID 10) is striping and mirroring together. This gives you the highest read and write performance of any of the raid options, but uses twice as many disks as normal.