Steve Lord schrieb:
> On Wed, 2002-08-14 at 12:08, Greg Freemyer wrote:
> > >> The normal way we setup something like this is to use a shared scsi
> > >> or fiberchannel disk setup, that way you no longer have a singe
> > >> point of failure. If you are putting the disks into one of the
> > >> two computers then if that system goes down you are dead in the
> > >> water. The other aspect of the above setup is using something
> > >> like failsafe, the two nodes monitor each other, and can (if
> > >> setup correctly) shoot the other node down and take over the
> > >> filesystem if it detects problems. failsafe itself is opensource,
> > >> not sure if the components of it which fail over the filesystem
> > >> to the other node are. Of course all this assumes using the fs
> > >> via NFS - the second node takes over the ip address of the failed
> > >> node.
> > >> A quick look at drbd on the net seems to show that it is designed
> > >> for these sorts of setups, and it has links to all the high
> > >> availability stuff for linux.
> > >> That aside, there should be no problem doing this, provided you
> > >> make sure the unmount from one system is complete before attempting
> > >> to mount on the other system. Mounting a filesystem which is
> > >> already mounted elsewhere is not a good thing, the second system
> > >> will think the fs needs recovery running on it.
> > >> Steve
> > I don't think drbd is designed for use in a shared SCSI environment.
> I did not intend to imply it was, just presenting a different way
> to build a resilient configuration.
> > It is more of a RAID 1 driver where the 2 halves of the mirror are on the 2
> > different servers using internal disks.
> > I believe it has support for ordered writes, but I for one would not simply
> > assume XFS and drbd are compatible.
> Ah, I should have read more.... if the fs is mirrored between the two
> hosts then there is a chance it will work OK. However, the interesting
> part of XFS is write ordering - there are certain writes which we need
> to know have made it down to disk and will survive a crash. In this
> sort of setup I really do not know where the data will be once drbd
> says it is written. Probably still in cache on the remote box for a
> start. There may well be circumstances where loss of both machines
> will cause filesystem corruption.
> you are right, testing such a setup before going live with it is
> important, please do not take my comments as meaning it will definitely
If I'm not completely wrong here drbd is similar to nbd, isn't it.
Long time ago I have successfully built a software RAID5 over three
server using nbd, of course running XFS as filesystem.
> > Greg Freemyer
> > Internet Engineer
> > Deployment and Integration Specialist
> > Compaq ASE - Tru64 v4, v5
> > Compaq Master ASE - SAN Architect
> > The Norcross Group
> > www.NorcrossGroup.com
> Steve Lord voice: +1-651-683-3511
> Principal Engineer, Filesystem Software email: lord@xxxxxxx