I'm setting up a CentOS 5 server that will be connected to an HP EVA4000. My previous experience is with an HP VA7400 and HP-UX. In HP-UX I can add "alternate paths" to a volume group in order to have redundant paths to the SAN via dual fiber channel HBAs just by either adding them with 'vgextend' or appending the appropriate PV paths when using 'vgcreate'. I tried doing something similar in CentOS with 'vgextend' and got some errors about duplicate PV ids. The LUN (a single one) I create on the EVA4000 show up on the CentOS box as /dev/sda, /dev/sdb, /dev/sdc, /dev/sdd. And when I partitioned /dev/sda so that I had /dev/sda1, I also saw that /dev/sdb1, /dev/sdc1 and /dev/sdd1 were automagically there. So I know that these extra devices reflect the dual fiber channel HBAs and the dual paths through our redundant fiber switches.
My question is... did I do this the right way? When I do a 'vgdisplay' now I get:
Code:
[root@localhost ~]# vgdisplay
Found duplicate PV Up921bgzWK4I7xtw7JiOB3VrdbVZhH2Z: using /dev/disk/by-path/pci-0000:13:00.0-fc-0x50001fe1500ca568:0x0001000000000000-part1 not /dev/sda1
Found duplicate PV Up921bgzWK4I7xtw7JiOB3VrdbVZhH2Z: using /dev/disk/by-id/scsi-3600508b400070ac40000900000090000-part1 not /dev/disk/by-path/pci-0000:13:00.0-fc-0x50001fe1500ca568:0x0001000000000000-part1
at the beginning of the expected output. I want to avoid having to test the redundancy by disconnecting the fiber if possible. And in all honesty I don't think this is the right way to set up redundant paths on CentOS (or any other Linux distro for that matter). I think the "alternate paths" functionality is specific to HP-UX's implementation of LVM. But I suspect there is a "right way" to do alternate paths on Linux for redundancy.
