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Trying to configure failover in multipath.conf

Posted on 2013-01-10
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Last Modified: 2013-01-15
Hello,

I am trying to configure multipathing to our storage with a failover policy. At the minute it looks like it's set to round robin, which is not what we want at the moment.

If I do a multipath-ll command I seem to have two active paths. Please see below

mpath0 (36000eb335cd762ff00000000000005c4) dm-2 IBM,iSCSIDisk
[size=500G][features=1 queue_if_no_path][hwhandler=0][rw]
\_ round-robin 0 [prio=2][active]

 \_ 1:0:0:0 sda 8:0   [active][ready]
 \_ 2:0:0:0 sdh 8:112 [active][ready]

I would expect one to be [active][ready] and the other to be [active][standby] ??

My multipath.conf file is configured as follows

devices {
        device {
                vendor                           "IBM"
                product                          "iSCSIDisk"
                path_grouping_policy      failover
                getuid_callout                "/sbin/scsi_id -g -u -s /block/%n"
                path_checker                  readsector0
                path_selector                "round robin 0"
                hardware_handler         "0"
                failback                          immediate
                rr_weight                       priorities
                no_path_retry                queue
        }

Am I missing something?
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Question by:vmdude
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arnold earned 500 total points
ID: 38763978
Your selector option is round robin.
Of you want it to be ins failback mode, that is the setup you need to create.

Are you encountering issue with round robin? Round robin may increase the available throughput.
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by:vmdude
ID: 38764049
Many thanks for the reply. No issue with round robin, we have very good throughput,  but really want the failover. I'll give your suggestion a go and update here shortly
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by:vmdude
ID: 38764085
Thanks, however, I'm not sure what selector would help me make one path active and one path standby/passive. As far as I can see there are only 3 types of path selector:


round-robin 0: Loop through every path in the path group, sending the same amount of I/O to each.

queue-length 0: Send the next bunch of I/O down the path with the least number of outstanding I/O requests.

service-time 0: Send the next bunch of I/O down the path with the shortest estimated service time, which is determined by dividing the total size of the outstanding I/O to each path by its relative throughput.

The default value is round-robin 0.

Which one should I do?
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by:arnold
arnold earned 500 total points
ID: 38764107
The difference deals with whether the devices are part of the same group or they are added individually.
http://www.netfibre.com/?p=447
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by:vmdude
ID: 38764131
Perfect! That like helps a lot. I'll post my findings back here shortly
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