On Sun, 2002-02-10 at 22:38, Jason Lim wrote: > Okay, as you said, with RAID10 and 4 40G HDs, usable space is 80Gs. > > On the other hand, with RAID5 and 3 40G HDs, usable space is also 80Gs, > with 1 spare HD for rebuilding. > > The question becomes... which provides more performance and is more > reliable?
RAID10 will give you the most performance. Not only do you have 4 disks working for you all the time, instead of 3 with RAID5, you (or more accurate: your CPU) also don't have to calculate the parity which is used by RAID5. Both will survive a 1 disk crash with no problems and both will appear as a RAID0 array when running in degraded mode. However, the reliability is different when a second disk fails. In RAID5 with spare you are out of luck when a second disk fails while the spare is rebuilding. With RAID10 and 1 failed disk, you only have the disk that is in the same stripe as the failed disk that is save to fail. I'm not sure if the raid card supports a stripe of two mirrors. This setup will survive a 2 disk failure. -- Tot ziens, Bart-Jan
