Re: Adding spare drive

[Derek Vadala <derek@cynicism.com>]

On Mon, 6 May 2002, mousebusiness.com wrote:

> I will be building a RAID5 array with 5 data drives and one hot spare. I
> need to use the drive for hot spare for something else at the moment. Is it
> possible to build my array with 5 drives and add hot spare later by simply
> adding the entry for it in /etc/raidtab?

Just create a 5-disk RAID-5 without a hot spare. When you're ready to
bring the spare disk into the array just use raidhotadd to insert it.

# raidhotadd /dev/md0 /dev/<sparedevice>

Now <sparedevice> is a spare disk in /dev/md0 (the 5-disk RAID-5). Now
update /etc/raidtab to reflect the new config. That means you'll add
nr-spare-disks and a device/spare-disk entry for /dev/<sparedevice>.

You can raidstop and raidstart the array to make sure it works, if it
makes you feel better, but you shouldn't need to.

> The array will be built with 6 drives connected to 3 IDE controllers, one
> per channel, 2 channels on each board. If one controller fails, obviously
> the array will go down with it. Does that mean that all data will be
> irrecoverably lost or will things go back to normal after I replace
> defective controller and let the array resync?

You'll be able to recover from a controller failure by replacing the
failed controller. Since physical controller placement typically impacts
device names you want to make sure you put a new controller in the same
slot as the one the failed, or make sure you have mapped out the disk
order and changed /etc/raidtab to reflect any changes.

---
Derek Vadala, derek@cynicism.com, http://www.cynicism.com/~derek