Re: Software raid OK?

[Mark Allums <mark@allums.com>]

Michael Iatrou wrote:
> When the date was Monday 20 April 2009, Douglas A. Tutty wrote:
>
> > On Mon, Apr 20, 2009 at 03:29:00PM +0300, Michael Iatrou wrote:
> > > When the date was Monday 20 April 2009, BAGI Akos wrote:
> > > > Hi List!
> > > >
> > > > I installed a software raid, level1 with 3 disks, one of them is a
> > > > spare.
> > > >
> > > > I have 2 partitions:
> > > > md0 is for / and is made of sda1,sdb1, sdc1
> > > > md1 is for swap and made of sda2,sdb2, sdc2
> > > There is no particularly good reason to have the swap on RAID. You
> > > should define three independed swap partitions; if disk fails, kernel
> > > will use the other available.
> > If swap fails, what happens if something important to the running of the
> > system (not just a user app) is swapped-out?  I've seen advice on this
> > list many times that to avoid a crash, if other system stuff is on raid,
> > that swap should be as well.
>
> I cannot confirm that; instead I am assuming a workflow like the following:
>
> 1. A disk is about to fail
> 2. Notification from SMART hits sysadmin's mailbox
> 3. # swapoff /dev/sdXY
> 4. Replace disk, create partitions
> 5. # swapon /dev/sdXY
> 6. # mdadm /dev/mdK -a /dev/sdXZ

Relying on S.M.A.R.T. is playing with atomic bombs.  Put everything on 
redundant storage, even swap.

Mark Allums