Nick Holland wrote: > Welcome to the REALITY of RAID. > > If you rely on RAID to always work, and never go down, you Just Don't > Understand. > > ... > > If hardware breaks, don't expect everything else to keep working. Hope, > sure. Expect? No. I don't care if you are talking about ccd, > RAIDframe, or hardware RAID. Your machine can still go down due to a > disk failure. People who don't believe me have just been lucky. So far.
> Further, if you wait until a disk fails to find out how things work, you > are a fool. Worst down-time disasters I've seen involved RAID systems > where people expected magic to happen when something went wrong. I come from a mainframe world that deals in non stop transaction processing. That world expects disks to die, and the system to keep on running. Hardware mirroring is done within a disk controller, and software mirroring is done between controllers. Software mirror is done largely to protect from controller failure, not disk failure. It is the norm in such an environment to add and remove disks and disk controllers on the fly. Now, I know I should not expect the reliability on a pc vs. a mainframe, but I have had twice had disks fail on Windows servers using software mirroring and both times those systems survived. For about the last three years, whenever I order workstation I always spend a bit extra to get mirroring. (Its about $25 extra plus the price of the disk drive) I also advise everyone I know to do the same. I have yet to have a windows machine die because of a disk failure when mirrored. I have also yet to see any loss of data. I have had many people thank me for my advise. I am careful when I set up a software raid. The two disk must be on separate IDE controllers. The master/slave jumpers screw up when one disk dies. Even cable select seems to cause troubles. My believe is if a system dies, as a result of a mirrored disk's death on a properly configured system, there is bug. I chose OpenBSD for its security, I use it for my name servers, fire wall, mail and web, and I have set others up with it for the same reason. I completely believe that OpenBSD is the best choice for protecting again intrusion. I just wish my data was more security against its loss. P.S. For some strange reason, Microsoft allows mirror, stripping and concatenation, with disk on the server, but the work station only allow stripping and concatenation. So hardware mirror is the only option for XP. I prefer software mirroring, because it allows for controller failure. I have had a hardware raid system controllers failure and write garbage over the disks. I have also had a power supply screw up and cause multiple disk failure on another hardware raid system. Recently I have seen a lot of ide controller failures. If you use raid you still have to do backups!
