Multipath timeout

Multipath timeout

[Isidro Hortelano]

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Hi list,

I have the current configuration of multipath :

defaults {
         polling_interval      5
         user_friendly_names   yes
         find_multipaths       yes


}

blacklist {
        devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"
        devnode "^hd[a-z]"
        devnode "^dcssblk[0-9]*"

        device {
                vendor "HP"
                product "LOGICAL VOLUME.*"
        }

        device {
                vendor "DGC"
                product "LUNZ"
        }

}
devices {
             device {
                vendor                  "3PARdata"
                product                 "VV"
                path_grouping_policy group_by_prio
                path_selector "round-robin 0"
                path_checker tur
                features "0"
                hardware_handler "1 alua"
                prio alua
                failback immediate
                rr_weight uniform
                no_path_retry 2
                rr_min_io_rq 1
                detect_prio yes
                fast_io_fail_tmo 10
                dev_loss_tmo 14
        }
}

I have a scsi timeout of 30 sec. by default, with this configuration how
much time does the multipath wait for an answer from a scsi command issued?
Regards,

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Re: Multipath timeout

[Martin Wilck]

On Tue, 2017-03-21 at 15:48 +0100, Isidro Hortelano wrote:
> I have a scsi timeout of 30 sec. by default, with this configuration
> how much time does the multipath wait for an answer from a scsi
> command issued?

The SCSI timeout also applies to the TUR commands sent by multipathd,
so that's about the time it would wait, plus/minus a few seconds
(multipathd doesn't try to be accurate). Note that you can set the
"checker_timeout" configuration option to modify the timeout value.

If other ("normal") SCSI commands time out, and the kernel error
handling results in failing the path, multipathd will be notified by an
DM event. But the kernel will not necessarily fail the path immediately
after a command timeout.

Regards
Martin


-- 
Dr. Martin Wilck <mwilck@suse.com>, Tel. +49 (0)911 74053 2107
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)

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