On Tue, 2005-09-06 at 20:06 -0400, Steve Wilcox wrote: > On Wed, 2005-09-07 at 00:57 +0200, Andreas Brosche wrote: > > > > - Multi-initator SCSI buses do not work with GFS in any meaningful way, > > > regardless of what the host controller is. > > > Ex: Two machines with different SCSI IDs on their initiator connected to > > > the same physical SCSI bus. > > > > Hmm... don't laugh at me, but in fact that's what we're about to set up. > > > > I've read in Red Hat's docs that it is "not supported" because of > > performance issues. Multi-initiator buses should comply to SCSI > > standards, and any SCSI-compliant disk should be able to communicate > > with the correct controller, if I've interpreted the specs correctly. Of > > course, you get arbitrary results when using non-compliant hardware... > > What are other issues with multi-initiator buses, other than performance > > loss? > > I set up a small 2 node cluster this way a while back, just as a testbed > for myself. Much as I suspected, it was severely unstable because of > the storage configuration, even occasionally causing both nodes to crash > when one was rebooted due to SCSI bus resets. I tore it down and > rebuilt it several times, configuring it as a simple failover cluster > with RHEL3 and RHEL4, a GFS cluster under RHEL4 and Fedora4, and as an > openSSI cluster using Fedora3. All tested configurations were equally > crash-happy due to the bus resets. > > My configuration consisted of a couple of old Compaq deskpro PC's, each > with a single ended Symbiosis card (set to different SCSI ID's > obviously) and an external DEC BA360 jbod shelf with 6 drives. The bus > resets might be mitigated somewhat by using HVD SCSI and Y-cables with > external terminators, but from my previous experience with other > clusters that used this technique (DEC ASE and HP-ux service guard), bus > resets will always be a thorn in your side without a separate, > independent raid controller to act as a go-between. Calling these > configurations simply "not supported" is an understatement - this type > of config is guaranteed trouble. I'd never set up a cluster this way > unless I'm the only one using it, and only then if I don't care one > little bit about crashes and data corruption. My two cents. > > -steve Small clarification - Although clusters from DEC, HP, and even DigiComWho?Paq's TruCluster can be made to work (sort of) on multi- initiator SCSI busses, IIRC it was never a supported option for any of them (much like RedHat's offering). I doubt any sane company would ever support that type of config. -steve -- Linux-cluster@xxxxxxxxxx http://www.redhat.com/mailman/listinfo/linux-cluster
