In the mean time, while waiting for further answers, I successfully
tested the failover group policy config
My way of proceedings was this, hope correct.
I didn't find any mention of IBM 1814 in multipath.conf.annotated...
I did find inside it
#defaults {
...
# # name : path_grouping_policy
# # scope : multipath
# # desc : the default path grouping policy to apply to unspecified
# # multipaths
# # values : failover = 1 path per priority group
# # multibus = all valid paths in 1 priority group
# # group_by_serial = 1 priority group per detected serial
# # number
# # group_by_prio = 1 priority group per path priority
# # value
# # group_by_node_name = 1 priority group per target node name
# # default : failover
# #
# path_grouping_policy multibus
this seemed a bit misleading because it is not clear to me if the
default then would be multibus or failover...
Setting failover as the group policy inside the defaults {} section of
multipath.conf didn't work.
defaults {
user_friendly_names yes
path_grouping_policy failover
}
.. probably overwritten by device itself config default?
Anyway I tried another "path"
# multipahd -k
multipathd> show config
...
found now IBM 1814 inside the output with these specs (donna if would
have found a similar result in a more general section in
multipath.conf.annotated ...)
#devices {
# device {
# vendor "IBM"
# product "1814"
# path_grouping_policy group_by_prio
# getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
# path_selector "round-robin 0"
# path_checker rdac
# features "0"
# hardware_handler "1 rdac"
# prio_callout "/sbin/mpath_prio_rdac /dev/%n"
# failback immediate
# rr_weight uniform
# no_path_retry queue
# rr_min_io 1000
# }
#
So I wanted only to change the path_grouping_policy parameter and I
set this in my multipath.conf
devices {
device {
vendor "IBM"
product "1814"
path_grouping_policy failover
}
}
Then
# multipath -v2 -d
and then committed (after deactivating fs and VG, donna if necessary...) with
# multipath -v2
Now I have indeed:
# multipath -l
mpath1 (3600a0b80005012440000093e4a55cf33) dm-6 IBM,1814 FAStT
[size=3.4T][features=1 queue_if_no_path][hwhandler=0][rw]
\_ round-robin 0 [prio=0][enabled]
\_ 3:0:0:1 sdb 8:16 [active][undef]
\_ round-robin 0 [prio=0][enabled]
\_ 4:0:0:1 sdc 8:32 [active][undef]
\_ round-robin 0 [prio=0][enabled]
\_ 3:0:1:1 sdd 8:48 [active][undef]
\_ round-robin 0 [prio=0][enabled]
\_ 4:0:1:1 sde 8:64 [active][undef]
Tried this command
# time dd if=/dev/zero of=testfile2 bs=1024k count=102400
102400+0 records in
102400+0 records out
107374182400 bytes (107 GB) copied, 651.872 seconds, 165 MB/s
real 10m51.934s
user 0m0.048s
sys 3m41.549s
And iostat confirmed only sdb was used during I/O operation
I got about 5% performance gain, as yesterday
# time dd if=/dev/zero of=testfile bs=1024k count=102400
102400+0 records in
102400+0 records out
107374182400 bytes (107 GB) copied, 686.96 seconds, 156 MB/s
real 11m27.010s
user 0m0.070s
sys 3m33.813s
But it could also be related to different I/O going through the DS4700 today.
BTW: I would expect "multipathd -k" --> show config to be updated
after changing the policy, but it continues to give
path_grouping_policy group_by_prio
for the IBM 1814
Probably it is a static display... any way to show the current one
with this command?
Sorry for the many answers... probably more targeted at dm-user ml...
Gianluca
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