66 lines
2.6 KiB
Diff
66 lines
2.6 KiB
Diff
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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Benjamin Marzinski <bmarzins@redhat.com>
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Date: Mon, 4 Jan 2021 21:59:55 -0600
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Subject: [PATCH] multipath.conf.5: Improve checker_timeout description
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I was asked to explain how checker_timeout works for checkers like
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directio, that don't issue scsi commands with an explicit timeout.
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Also, undeprecate the directio checker.
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Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
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Reviewed-by: Martin Wilck <mwilck@suse.com>
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Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
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---
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multipath/multipath.conf.5 | 20 ++++++++++++--------
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1 file changed, 12 insertions(+), 8 deletions(-)
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diff --git a/multipath/multipath.conf.5 b/multipath/multipath.conf.5
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index ea66a01e..8ef3a747 100644
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--- a/multipath/multipath.conf.5
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+++ b/multipath/multipath.conf.5
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@@ -472,8 +472,12 @@ The default is: \fB<unset>\fR
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.
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.TP
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.B path_checker
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-The default method used to determine the paths state. Possible values
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-are:
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+The default method used to determine the path's state. The synchronous
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+checkers (all except \fItur\fR and \fIdirectio\fR) will cause multipathd to
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+pause most activity, waiting up to \fIchecker_timeout\fR seconds for the path
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+to respond. The asynchronous checkers (\fItur\fR and \fIdirectio\fR) will not
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+pause multipathd. Instead, multipathd will check for a response once per
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+second, until \fIchecker_timeout\fR seconds have elapsed. Possible values are:
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.RS
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.TP 12
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.I readsector0
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@@ -499,10 +503,8 @@ Check the path state for LSI/Engenio/NetApp RDAC class as NetApp SANtricity E/EF
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Series, and OEM arrays from IBM DELL SGI STK and SUN.
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.TP
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.I directio
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-(Deprecated) Read the first sector with direct I/O. If you have a large number
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-of paths, or many AIO users on a system, you may need to use sysctl to
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-increase fs.aio-max-nr. This checker is being deprecated, it could cause
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-spurious path failures under high load. Please use \fItur\fR instead.
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+Read the first sector with direct I/O. This checker could cause spurious path
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+failures under high load. Increasing \fIchecker_timeout\fR can help with this.
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.TP
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.I cciss_tur
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(Hardware-dependent)
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@@ -639,8 +641,10 @@ The default is: \fBno\fR
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.
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.TP
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.B checker_timeout
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-Specify the timeout to use for path checkers and prioritizers that issue SCSI
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-commands with an explicit timeout, in seconds.
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+Specify the timeout to use for path checkers and prioritizers, in seconds.
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+Only prioritizers that issue scsi commands use checker_timeout. If a path
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+does not respond to the checker command after \fIchecker_timeout\fR
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+seconds have elapsed, it is considered down.
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.RS
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.TP
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The default is: in \fB/sys/block/sd<x>/device/timeout\fR
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--
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2.17.2
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