Steve Wilcox wrote: > 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 > HP-UX ServiceGuard words well with multi-initiator SCSI configurations, and is fully supported by HP. It is sold that way for small 2-4 node clusters when cost is an issue, although FC has become a big favorite (um...money maker) in recent years. Yes, SCSI bus resets are a pain, but they are handled by HP-UX, not ServiceGuard. --Keith
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