OK, why RAID 10 is more secure than RAID 5 (with or without the hot spare). Lets say we have 6 drives we want to RAID. In a RAID 10 they would be set up like this:
where 1&2, 3&4 and 5&6 are individual mirrors striped together in a RAID 0. If each mirror lost a drive (say 2,3 and 6) the array would still function but if a RAID 5 loses more than one disk the whole array is toast. Since you can add a hot spare to either array type the security of either would be boosted the same. There is still the chance that both drives in a mirror would fail, but figured in with the rest it still gives RAID 10 a better chance of surviving than RAID 5. Another advantage is higher overall performance since parity data isn't being calculated during each write. The biggest drawback to RAID 10 is you lose half your disk space. (But I'm sure you knew that already
The parity data of a RAID 5 is really only used in the event of a drive failure, using just
parity data to determine if a bit is bad would be difficult (how would it know which
bit is bad?). The array card uses the error detection built into the drive iself and rebuilds the data based on what it knows is bad, and that would work in either array configuration. Another thing about RAID 5 is the more drives you add, the bigger chance that more than one would die; eventually it would become less reliable than a single drive. Personally I become wary of arrays bigger than 8 drives, after that it's usually better to create two separate arrays.
<font size=-1>[ This Message was edited by: Steel on 2002-03-27 23:09 ]</font>
<font size=-1>[ This Message was edited by: Steel on 2002-03-27 23:10 ]</font>