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Increase default zfs_multihost_fail_intervals and import_intervals 

By default, when multihost is enabled for a pool, the pool is
suspended if (zfs_multihost_fail_intervals*zfs_multihost_interval) ms
pass without a successful MMP write.  This is the recommended
configuration.

The default value for zfs_multihost_fail_intervals has been 5, and the
default value for zfs_multihost_interval has been 1000, so pool
suspension occurred at 5 seconds.

There have been multiple cases where a single misbehaving device in a
pool triggered a SCSI reset, and all I/O paused for 5-6 seconds.  This
in turn caused MMP to suspend the pool.

In the cases observed, the rest of the devices were healthy and the
pool was otherwise correctly performing I/O.  The reset was handled
correctly by ZFS, and by suspending the pool MMP made replacing the
device more difficult as well as forcing the host to be rebooted.

Increase the default value of zfs_multihost_fail_intervals to 10, so
that MMP tolerates up to 10 seconds of failed MMP writes before
suspending the pool.

Increase the default value of zfs_multihost_import_intervals to 20, to
maintain the 2:1 safety factor.  This results in a force import taking
approximately 20 seconds when MMP is enabled, with default values.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Andreas Dilger <andreas.dilger@whamcloud.com>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Olaf Faaland <faaland1@llnl.gov>
Closes #7709 
Closes #8495
This commit is contained in:
Olaf Faaland 2019-03-13 09:50:48 -07:00 committed by Brian Behlendorf
parent cffa8372f4
commit db2af93d72
2 changed files with 4 additions and 4 deletions
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4
include/sys/mmp.h
View File

@ -29,8 +29,8 @@ extern "C" {
#define MMP_MIN_INTERVAL 100 /* ms */
#define MMP_DEFAULT_INTERVAL 1000 /* ms */
#define MMP_DEFAULT_IMPORT_INTERVALS 10
#define MMP_DEFAULT_FAIL_INTERVALS 5
#define MMP_DEFAULT_IMPORT_INTERVALS 20
#define MMP_DEFAULT_FAIL_INTERVALS 10
typedef struct mmp_thread {
kmutex_t mmp_thread_lock; /* protect thread mgmt fields */

4
man/man5/zfs-module-parameters.5
View File

@ -1879,7 +1879,7 @@ the risk of failing to detect an active pool. The total activity check time is
never allowed to drop below one second. A value of 0 is ignored and treated as
if it was set to 1
.sp
Default value: \fB10\fR.
Default value: \fB20\fR.
.RE
.sp
@ -1900,7 +1900,7 @@ will cause the pool to be suspended. This occurs when
passed since the last successful multihost write. This guarantees the activity test
will see multihost writes if the pool is imported.
.sp
Default value: \fB5\fR.
Default value: \fB10\fR.
.RE
.sp