Correct setup for multipath on RHEL 5.7 with EMC Clariion SAN / ALUA mode
Hi,
I'm building a set of RHEL 5.7 servers on Cisco UCS hardware with an EMC SAN (ALUA/type 4 mode).
With default multipathd config I experience I/O errors when accessing the passive/low prirority paths directly.
However if I disable the "healthy" paths access to the multipath device works as expected.
I have tried various configuration settings based on the following documents:
- https://bugzilla.redhat.com/show_bug.cgi?id=482737
- https://access.redhat.com/kb/docs/DOC-47889
- https://access.redhat.com/kb/docs/DOC-48959
This is my current configuration:
device {
vendor "DGC "
product ".*"
path_grouping_policy group_by_prio
getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
prio_callout "/sbin/mpath_prio_emc /dev/%n"
path_checker emc_clariion
path_selector "round-robin 0"
features "1 queue_if_no_path"
no_path_retry 300
hardware_handler "1 alua"
failback immediate
}
device {
vendor "DGC "
product ".*"
path_grouping_policy group_by_prio
getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
prio_callout "/sbin/mpath_prio_emc /dev/%n"
path_checker emc_clariion
path_selector "round-robin 0"
features "1 queue_if_no_path"
no_path_retry 300
hardware_handler "1 alua"
failback immediate
}
device {
vendor "DGC "
product ".*"
path_grouping_policy group_by_prio
getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
prio_callout "/sbin/mpath_prio_emc /dev/%n"
path_checker emc_clariion
path_selector "round-robin 0"
features "1 queue_if_no_path"
no_path_retry 300
hardware_handler "1 alua"
failback immediate
}
device {vendor "DGC "product ".*"path_grouping_policy group_by_priogetuid_callout "/sbin/scsi_id -g -u -s /block/%n"prio_callout "/sbin/mpath_prio_emc /dev/%n"path_checker emc_clariionpath_selector "round-robin 0"features "1 queue_if_no_path"no_path_retry 300hardware_handler "1 alua"failback immediate}
My multipath devices show up as this:
mpath2 (36006016085102d00be0d0344ebdde011) dm-2 DGC,VRAID
[size=20G][features=1 queue_if_no_path][hwhandler=1 emc][rw]
\_ round-robin 0 [prio=2][active]
\_ 0:0:1:16 sdi 8:128 [active][ready]
\_ 1:0:1:16 sdo 8:224 [active][ready]
\_ round-robin 0 [prio=0][enabled]
\_ 0:0:0:16 sdd 8:48 [active][ready]
\_ 1:0:0:16 sdk 8:160 [active][ready]
mpath2 (36006016085102d00be0d0344ebdde011) dm-2 DGC,VRAID[size=20G][features=1 queue_if_no_path][hwhandler=1 emc][rw]\_ round-robin 0 [prio=2][active]\_ 0:0:1:16 sdi 8:128 [active][ready]\_ 1:0:1:16 sdo 8:224 [active][ready]\_ round-robin 0 [prio=0][enabled]\_ 0:0:0:16 sdd 8:48 [active][ready]\_ 1:0:0:16 sdk 8:160 [active][ready]
(I get I/O errors reported on boot time, also if I try to do I/O to the pri 0 group devices I get I/O errors - but they work OK if I disable the pri 2 devices).
Are the I/O errors I see real or can they be ignored? What would a correct multipath configuration for this setup be?
Martin
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