On Thu November 13 2008 6:40:15 am Amedee Van Gasse wrote:
On Wed, November 12, 2008 11:33, Richard wrote:
In my opinion Per, a 4 drive RAID 5 is exposed to 'degraded' operation very infrequently, and when it is, the odds of a 2nd drive failing are almost microscopic, so at a hardware level, a 3 or 4 drive RAID 5 is an acceptible risk.
If all drives are of identical make, model, batch and production date, then the risk is no longer microscopic. Also, what *caused* drive failure? If it's something like overheated hardware that makes one drive fail, the next drive will fail even sooner.
-- Amedee
There is merit in your caution, however I chose a single manufacture with a product that is NOT the latest, biggest drive they offer, opting for one whose design has been 'proven' (to me at least over a period of many years). I use WD 400G drives because in many years, I only had 1 failure (out of well over 20 drives, some retired due to the fact I simply needed more space, others still in use. That one failure was handled within 72 hours by them with no questionss asked and our drives 'crossed in the mail', quite literraly. The 400G drives were big enough in a 4 drive raid5 array to be useful, cheap enoough to make the 'I' in raId which to me has always meant I(nexpensive D(evices in the Redundant Array acronym. Proven design, reliable company and personal experience all pointed to going against your advice when I constructed my RAID 2 years ago initially. Since then, I have created a 2nd and 3rd in my computers at home. Shoot, I now have 12 drives in arrays at home and added to the previous 20 or so WD drives, I had / have a good feel for WD and that Caviar series of drives. I have recently had my 2nd failure of a drive....I had lost the AC in the room that had the machine with 9 drives in it and that drive simple got too hot and failed. Even so, I maintain that true simultaneous multi-drive failure is a microscopic, albeit non-zero, chance and worth the risk for home and most SOHO environments. I believe in good backup technology for the small, non-zero chance event. For larger businesses with more critical storeage needs and more critical reliabilty requirement, I would recommend raid 6 coupled with real-time (or nearly so) backups to an outside / external system. For really critical stuff, separate but real-time co-datacenters give that true warm fuzzy feeling about reliability and security. When I was responding to the OP (Per Jensen), I did not know what his requirements were so was forced to generalize, but I think the advice I offered was sound. Your advice/cautions are well taken, especially given that often people buy the cheapest, biggest, least-proven drives they can find. They often pay the higher price in the long run due to the very issues you brought up. Richard -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org