I'm using LVM2 with device-mapper-multipath 0.4.5 on GA RHEL 4 update 2
release, kernel version 2.6.9-22.ELsmp. Storage is 4 Clariion CX600
LUNs,
2 with a primary path on SP A and 2 on SP B. HBAs are QLA3240 with
firmware 3.03.15 IPX and the RedHat-distributed driver version
8.01.00b5-rh2.
When I disrupt one path by disabling a host or SP switch port,
failover works great but failback doesn't happen automatically
with the current config (below). By this I mean
when the connection to e.g. SP B is restored, all
4 LUNs stay trespassed to SP A. Is this by design?
Or is there support for automatic failback, i.e.
I/O is paused and a trespass is issued to restore
the 2 SP B LUNs to their primary paths?
Of course manual failback is possible, but without
quiescing I/O I found I was able to munge my LVM2
objects up quite nicely. Manual failback with quiesced
I/O is fine.
Here's the /etc/multipath.conf:
defaults {
multipath_tool "/sbin/multipath -v0"
udev_dir /dev
polling_interval 10
default_selector "round-robin 0"
default_path_grouping_policy multibus
default_getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
default_prio_callout "/bin/true"
default_features "0"
rr_wmin_io 100
failback immediate
}
devices {
device {
vendor "DGC "
product "RAID 5 "
#path_grouping_policy group_by_serial
path_grouping_policy failover
getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
path_checker emc_clariion
path_selector "round-robin 0"
features "0"
hardware_handler "1 emc"
}
}
Here's the multipath -l output (with both paths up)
and a few commands to help make sense of it:
[root@sandbox ~]# multipath -l
3600601604b600d00743e69d8862fda11
[size=1 GB][features="0"][hwhandler="1 emc"]
\_ round-robin 0 [active]
\_ 1:0:0:3 sdd 8:48 [active]
\_ round-robin 0 [enabled]
\_ 0:0:0:3 sdh 8:112 [active]
3600601604b600d00773e69d8862fda11
[size=4 GB][features="0"][hwhandler="1 emc"]
\_ round-robin 0 [active]
\_ 1:0:0:0 sda 8:0 [active]
\_ round-robin 0 [enabled]
\_ 0:0:0:0 sde 8:64 [active]
3600601604b600d00763e69d8862fda11
[size=3 GB][features="0"][hwhandler="1 emc"]
\_ round-robin 0 [active]
\_ 1:0:0:1 sdb 8:16 [active]
\_ round-robin 0 [enabled]
\_ 0:0:0:1 sdf 8:80 [active]
3600601604b600d00753e69d8862fda11
[size=2 GB][features="0"][hwhandler="1 emc"]
\_ round-robin 0 [active]
\_ 1:0:0:2 sdc 8:32 [active]
\_ round-robin 0 [enabled]
\_ 0:0:0:2 sdg 8:96 [active]
# ls -l /dev/mpath
total 0
lrwxrwxrwx 1 root root 7 Oct 21 12:56 3600601604b600d00743e69d8862fda11
-> ../dm-3
lrwxrwxrwx 1 root root 7 Oct 21 12:56 3600601604b600d00753e69d8862fda11
-> ../dm-2
lrwxrwxrwx 1 root root 7 Oct 21 12:56 3600601604b600d00763e69d8862fda11
-> ../dm-1
lrwxrwxrwx 1 root root 7 Oct 21 12:56 3600601604b600d00773e69d8862fda11
-> ../dm-0
# pvs
PV VG Fmt Attr PSize PFree
/dev/dm-0 vgtest2 lvm2 a- 4.00G 3.90G
/dev/dm-1 vgtest2 lvm2 a- 3.00G 2.90G
/dev/dm-2 vgtest2 lvm2 a- 2.00G 1.90G
/dev/dm-3 vgtest2 lvm2 a- 1020.00M 920.00M
Thanks in advance,
Phil Lowden
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