Re: devices in OST failover

On Apr 23, 2007  07:05 -0400, Brian J. Murrell wrote:
> On Mon, 2007-23-04 at 12:56 +0200, Hans Einar Gautun wrote:
> > I want to have a local /dev/sdaX on each OST - with same size. That
> > means:
> > 
> > ost1 with its own /dev/sda3
> >                              in an active/active failover with
> > ost2 with its own /dev/sda3
> > 
> > Is this possible, or have I misunderstanded something?
> 
> The purpose of failover is so that two OSSes can provide the same
> service to the lustre network.  That is, should one of the two nodes
> fail (i.e. a piano falls on it and completely destroys it), the other
> OSS can provide exactly the same services.
> 
> So you have to ask yourself, if you have a local disk in each machine
> and one machine gets crushed under a piano, how does other machine
> provide service from the crushed machine's disk?
> 
> There are two solutions.  Use a network replication service like drbd
> (so that the contents of the local disks is identical at all times) or
> use an external storage system that both OSSes can access, like FC SCSI
> or Firewire, etc.

And sometime in the future Lustre will support OST-level RAID, but that
is still some ways away.

Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.