RAC w/ASM - scanorder with EMC powerpath devices

for those of you running ASM on RHEL4, you might want to make sure the scanorder is setup properly in /etc/sysconfig/oracleasm.

I got called last week about a node being down on 2-node RAC SE with ASM.
node 1 was crashed and node 2 was running. the error in the logs said it had a corrupt control file. After looking into it a little bit more, I saw there was emergency SAN maintenance done around the same time.
suspicious, I kept looking around. It shouldn't have been a problem because we have redundancy built into it (dual HBAs, multiple paths to the EMC array...)
ASM was up and running, but trying to start the instance generated a bunch of errors.
Oracle said the controlfile was gone, but I didn't believe it because node2 was working.
the SAN admin and myself were talking about and I mentioned that we point to the pseudo device and not the real paths. That made want to go and double check. I looked at node 2 and it was using "emcpowera1" for asm.
I went over to node1 (crashed node) and it was using "sdb1" ( which was a path SPB that was replaced during maintenance). I looked at the oracleasm_scanorder and it was missing from node1. node2 had it set to "emcpower sd".
made the additional change and rebooted it. asm used it, but the cluster wouldn't come up. Oracle said it was in a split brain condition. I rebooted both nodes, ASM chose the emc power devices for both and both instances came up - no corrupt controlfile.

save yourself some trouble and verify it.

/etc/init.d/oracleasm listdisks

/etc/init.d/oracleasm querydisk <name from previous cmd>

# this step is a little bit of a pain because the spacing after the comma doesn't match. it's not hard to figure out though. #the output of this command should be the psuedo device "emcpower??"

ls -l /dev | grep 'xxx, xx'

I have another one with a similar setup, but it's with RHEL3. The ASM page (http://www.oracle.com/technology/tech/linux/asmlib/ multipath.html ) , it has the following comments about powerpath and 2.4 kernel.

EMC PowerPath and ASMLib
A lot of administrators want to use EMC PowerPath for multipathing and ASMLib for disk access.
However, PowerPath and the 2.4 kernels are not supported by EMC. Systems with the Linux 2.6 kernel, such as RHEL 4 or SLES 9, and the 2.0 ASMLib kernel driver are supported. Please reference the EMC Support Matrix to verify that any/all interoperability requirements are met.

If you have ANY issue related to support for ASMLib and PowerPath on systems using the Linux 2.4 kernel, such as RHEL 3 or SLES 8, please contact EMC.

I have some digging to do. I haven't found much information on ASM and rhel3.

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