Re: RAID 1/0 vs. RAID 5

Mike South wrote: > > I don't know about the Compaq RAID controller so I cannot say for > sure, however if it is a "smart" controller with read/write caching > RAID 5 should outperform RAID 1/0, because it automatically does > parallel reads AND writes are not adversely affected. Mike, any RAID 1/0 implementation worth the name also performs parallel reads and in addition can read from both sides of the mirror of each pair of drives so that there is MUCH less head movement and drive contention than in RAID 5. Also RAID 1/0 is almost 2x as fast as RAID 5 for writes and protects your data from bad media which RAID 5 cannot do. RAID 5 only saves you from catastrophic drive failure of a single drive. With RAID 1/0, properly set up with each side of the mirrors on separate controllers and power supplies you can loose a controller or power supply or up to 1/2 of your drives and still be running with VERY little degredation. In addition, recovering RAID5 from a single drive failure reduces performance up to 90% during recovery while a single drive RAID 1/0 failure will degrade performance during recovery by AT MOST (100 * 1/N)% where N is the number of mirrored pairs in the stripe set. Nope, RAID 1/0 will ALWAYS outperform RAID 5 in ALL aspects, it is just very darn expensive. Personnally my data and throughput are worth it, as is my sack time ;-) > >I am inclined to stick with RAID 1/0, but would appreciate any comments > >regarding performance and reliability of RAID 1/0 versus RAID 5, > >especially for complex queries. See above. Stick with RAID 1/0! Art S. Kagel