Re: Linux supports hot-swappable hardware? [was Re:

On Wed, 18 Jun 2003, Jonathan Bartlett wrote:

> > > As for SCSI disks and Power supplies, Linux supports hot swap. Check out
> > > Dell servers for example.
> >
> > Linux doesn't need to do anything to allow that, only the hardware needs
> > to.  It's kept away from the kernel by the RAID controller (in the case of
> > disks) or just not noticed in the PS department.
>
> This is true, however, Linux also, to some extent, support generic SCSI
> hotswap when the controller will handle it.

True.  There's actually some black art chicanery you can use to get a
SCSI driver to add a drive and such other than just rmmod / insmodding it.
I've played a bit with some of that stuff, and I don't think I'd ever do
it in production in the middle of the day.  Just wait til 10:00pm when the
load is the lightest and hope it works, and if it doesn't, the unmount the
partition, rmmod/insmod, remount, restart postgresql and you're gold.

I've found that while it's a little harder to hot swap individual disks in
linux using sw RAID, the ability to make the raid behave exactly as I want
is worth it.  Having lost a RAID5 set to a hw controller that simply had
the cable to two drives come loose but refused to accept them back into
the RAID5 after that without formatting them first, I'm no longer as wild
about hw raid controllers as I once was.