Bill said...
> Glenn is right. I like disk mirroring. I have seen big problems with > raid-5. When one of the Raid-5 disks dies, the whole RAID set is > worthless > as all of the data on the disks becomes invisible. > Hmmmm - the whole RAID 5 set is worthless when one disk dies? Isn't the whole point of a raid 5 stripe that one disk can die and the set will continue just fine albeit with zero redundancy? >From the wikipedia page on RAID (hopefully more accurate than the page on Jimmy Wales' girlfriend). Distributed parity requires all but one drive to be present to operate; drive failure requires replacement, but the array is not destroyed by a single drive failure. 'nuff said. Glen said... > > Why did you choose RAID5? RAID10 offers the redundancy you want from > RAID5, > but it won't grind to a snails pace when one of the drives fail. It > requires > more drives, but it gives more performance and reliability over RAID5. > > YMMV on this one. I agree RAID 1+0 is better but the last couple of drive failures I have experienced in a RAID 5 set have not had any noticeable impact. In fact the raid 5 set has held good performance while providing disk I/O and allowing the hot spare to bind into the set. Possibly a slight drop-off but definitely not snail's pace. However this is on an EMC San providing storage to RHEL servers so there is some serious caching going on there, although, IIRC the SAN will automatically disable write caching for an array with a failed disk. No idea what would happen with a raid-5 stripe in the built in scsi controllers in an HP DL though. Regards, Adrian Auckland, NZ ------- u2-users mailing list [email protected] To unsubscribe please visit http://listserver.u2ug.org/
