Forum OpenACS Q&A: Re: Switching to Raid 1...

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Posted by Ola Hansson on
Lars,

I have never experienced a hard drive crash using a RAID array, but I have _simulated one_ by powering off a box running with a working mirror, unplugging the power cord to one of the (IDE) drives and taking the system back up again. The mirror will "heal" transparently in the background; all I have to do is say:

raidhotadd /dev/md0 /dev/hda1
raidhotadd /dev/md1 /dev/hda2
raidhotadd /dev/md2 /dev/hda3
In reality, though, what happens in my case is that if I unplug hda (master no. 1, first half of mirror) and pretend it is broken, the BIOS of my mobo is too dumb to realize it should boot off of hde (master no. 2, second half of the mirror)... My guess is there are BIOSs that can handle this issue, though.

As long as the working part of the mirror is placed in the first IDE slot and a new replacement drive (of aproximately the same size) is in place (it too as a master), the box will boot, assuming lilo (or grub) has been correctly installed in the boot sector or boot partition of BOTH of the original drives. (The new drive will be bootable as the partitions get copied to it during healing)

Software RAID, too (just like most hardware RAID-solutions I,ve read about), lets you use n number of "hot spares" that will jump in transparantly in case of a failure in the mirror...