diff options
Diffstat (limited to 'man/man5/zfs-module-parameters.5')
| -rw-r--r-- | man/man5/zfs-module-parameters.5 | 56 |
1 files changed, 32 insertions, 24 deletions
diff --git a/man/man5/zfs-module-parameters.5 b/man/man5/zfs-module-parameters.5 index f75f09917..c1994f340 100644 --- a/man/man5/zfs-module-parameters.5 +++ b/man/man5/zfs-module-parameters.5 @@ -1849,20 +1849,14 @@ Default value: \fB0\fR. .ad .RS 12n Used to control the frequency of multihost writes which are performed when the -\fBmultihost\fR pool property is on. This is one factor used to determine -the length of the activity check during import. +\fBmultihost\fR pool property is on. This is one factor used to determine the +length of the activity check during import. .sp -The multihost write period is \fBzfs_multihost_interval / leaf-vdevs\fR milliseconds. -This means that on average a multihost write will be issued for each leaf vdev every -\fBzfs_multihost_interval\fR milliseconds. In practice, the observed period can -vary with the I/O load and this observed value is the delay which is stored in -the uberblock. -.sp -On import the activity check waits a minimum amount of time determined by -\fBzfs_multihost_interval * zfs_multihost_import_intervals\fR. The activity -check time may be further extended if the value of mmp delay found in the best -uberblock indicates actual multihost updates happened at longer intervals than -\fBzfs_multihost_interval\fR. A minimum value of \fB100ms\fR is enforced. +The multihost write period is \fBzfs_multihost_interval / leaf-vdevs\fR +milliseconds. On average a multihost write will be issued for each leaf vdev +every \fBzfs_multihost_interval\fR milliseconds. In practice, the observed +period can vary with the I/O load and this observed value is the delay which is +stored in the uberblock. .sp Default value: \fB1000\fR. .RE @@ -1876,8 +1870,17 @@ Default value: \fB1000\fR. Used to control the duration of the activity test on import. Smaller values of \fBzfs_multihost_import_intervals\fR will reduce the import time but increase 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 +never allowed to drop below one second. +.sp +On import the activity check waits a minimum amount of time determined by +\fBzfs_multihost_interval * zfs_multihost_import_intervals\fR, or the same +product computed on the host which last had the pool imported (whichever is +greater). The activity check time may be further extended if the value of mmp +delay found in the best uberblock indicates actual multihost updates happened +at longer intervals than \fBzfs_multihost_interval\fR. A minimum value of +\fB100ms\fR is enforced. +.sp +A value of 0 is ignored and treated as if it was set to 1. .sp Default value: \fB20\fR. .RE @@ -1888,17 +1891,22 @@ Default value: \fB20\fR. \fBzfs_multihost_fail_intervals\fR (uint) .ad .RS 12n -Controls the behavior of the pool when multihost write failures are detected. +Controls the behavior of the pool when multihost write failures or delays are +detected. .sp -When \fBzfs_multihost_fail_intervals = 0\fR then multihost write failures are ignored. -The failures will still be reported to the ZED which depending on its -configuration may take action such as suspending the pool or offlining a device. +When \fBzfs_multihost_fail_intervals = 0\fR, multihost write failures or delays +are ignored. The failures will still be reported to the ZED which depending on +its configuration may take action such as suspending the pool or offlining a +device. + .sp -When \fBzfs_multihost_fail_intervals > 0\fR then sequential multihost write failures -will cause the pool to be suspended. This occurs when -\fBzfs_multihost_fail_intervals * zfs_multihost_interval\fR milliseconds have -passed since the last successful multihost write. This guarantees the activity test -will see multihost writes if the pool is imported. +When \fBzfs_multihost_fail_intervals > 0\fR, the pool will be suspended if +\fBzfs_multihost_fail_intervals * zfs_multihost_interval\fR milliseconds pass +without a successful mmp write. This guarantees the activity test will see +mmp writes if the pool is imported. A value of 1 is ignored and treated as +if it was set to 2. This is necessary to prevent the pool from being suspended +due to normal, small I/O latency variations. + .sp Default value: \fB10\fR. .RE |