I was asked to explain how checker_timeout works for checkers like directio, that don't issue scsi commands with an explicit timeout. Also, undeprecate the directio checker.
Signed-off-by: Benjamin Marzinski <bmarz...@redhat.com> --- multipath/multipath.conf.5 | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) diff --git a/multipath/multipath.conf.5 b/multipath/multipath.conf.5 index ea66a01e..8ef3a747 100644 --- a/multipath/multipath.conf.5 +++ b/multipath/multipath.conf.5 @@ -472,8 +472,12 @@ The default is: \fB<unset>\fR . .TP .B path_checker -The default method used to determine the paths state. Possible values -are: +The default method used to determine the path's state. The synchronous +checkers (all except \fItur\fR and \fIdirectio\fR) will cause multipathd to +pause most activity, waiting up to \fIchecker_timeout\fR seconds for the path +to respond. The asynchronous checkers (\fItur\fR and \fIdirectio\fR) will not +pause multipathd. Instead, multipathd will check for a response once per +second, until \fIchecker_timeout\fR seconds have elapsed. Possible values are: .RS .TP 12 .I readsector0 @@ -499,10 +503,8 @@ Check the path state for LSI/Engenio/NetApp RDAC class as NetApp SANtricity E/EF Series, and OEM arrays from IBM DELL SGI STK and SUN. .TP .I directio -(Deprecated) Read the first sector with direct I/O. If you have a large number -of paths, or many AIO users on a system, you may need to use sysctl to -increase fs.aio-max-nr. This checker is being deprecated, it could cause -spurious path failures under high load. Please use \fItur\fR instead. +Read the first sector with direct I/O. This checker could cause spurious path +failures under high load. Increasing \fIchecker_timeout\fR can help with this. .TP .I cciss_tur (Hardware-dependent) @@ -639,8 +641,10 @@ The default is: \fBno\fR . .TP .B checker_timeout -Specify the timeout to use for path checkers and prioritizers that issue SCSI -commands with an explicit timeout, in seconds. +Specify the timeout to use for path checkers and prioritizers, in seconds. +Only prioritizers that issue scsi commands use checker_timeout. If a path +does not respond to the checker command after \fIchecker_timeout\fR +seconds have elapsed, it is considered down. .RS .TP The default is: in \fB/sys/block/sd<x>/device/timeout\fR -- 2.17.2 -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel
