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SAN devices get reordered every now and then
I'm running RHEL4u6 on most of my servers at work. We are connecting to SAN storage and using these devices as raw devices for Oracle and just for EXT3 file systems. We setup a cluster using VCS when i first noticed the problem. Server1 has two shared devices between Server2. On server1, it scanned the HBA bus and got two devices. emcpowera and emcpowerb. The same thing happend on server2 but for some reason, emcpowera was really emcpowerb and vice versa for emcpowerb. So server1 sees my storage in one order and server2 sees it in another order. The SAN team have verified that nothing on their end has to do with it as they just allocate the storage and that's it. It seems to be the linux kernel that has soemthing to do with this. Also, other things i've noticed is if we do a kernel upgrade, any devices that were down the line for example emcpowerR or emcpowerZ, re-order and the next boot and become emcpowerA, emcpowerB...etc...the reason they were emcpowerR and so forth was because we either moved it to another storage subsystem (same vendor) but this was due to a data center migration we had. Does anyone know a way that i can maybe have the kernel recognize the devices in the same order? Using UDEV maybe? or anywhere else i can be looking? We have kernel upgrades coming on our VCS clusters (Veritas Cluster Server) and we can't have the devices re-ordering on systems with 14 devices attached, it would be impossible to figure out if they are all attached to RAW devices used by Oracle. Any help will be truely appreciated. Thanks
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