3 files changed, 104 insertions, 5 deletions
diff --git a/man/man1/ztest.1 b/man/man1/ztest.1
index ebfacd46d..8cb07fa99 100644
--- a/man/man1/ztest.1
+++ b/man/man1/ztest.1
@@ -147,6 +147,12 @@ ztest -f / -V -T 120
 
 .SH "ENVIRONMENT VARIABLES"
 .TP
+.B "ZFS_HOSTID=id"
+Use \fBid\fR instead of the SPL hostid to identify this host.  Intended for use
+with ztest, but this environment variable will affect any utility which uses
+libzpool, including \fBzpool(8)\fR.  Since the kernel is unaware of this setting
+results with utilites other than ztest are undefined.
+.TP
 .B "ZFS_STACK_SIZE=stacksize"
 Limit the default stack size to \fBstacksize\fR bytes for the purpose of
 detecting and debugging kernel stack overflows.  This value defaults to
@@ -160,6 +166,7 @@ required for a NULL procedure in user space.
 
 By default the stack size is limited to 256K.
 .SH "SEE ALSO"
+.BR "spl-module-parameters (5)" ","
 .BR "zpool (1)" ","
 .BR "zfs (1)" ","
 .BR "zdb (1)" ","
diff --git a/man/man5/zfs-module-parameters.5 b/man/man5/zfs-module-parameters.5
index ab1c15841..0447debf7 100644
--- a/man/man5/zfs-module-parameters.5
+++ b/man/man5/zfs-module-parameters.5
@@ -1413,6 +1413,79 @@ Default value: \fB0\fR.
 .sp
 .ne 2
 .na
+\fBzfs_multihost_history\fR (int)
+.ad
+.RS 12n
+Historical statistics for the last N multihost updates will be available in
+\fB/proc/spl/kstat/zfs/<pool>/multihost\fR
+.sp
+Default value: \fB0\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_multihost_interval\fR (ulong)
+.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.
+.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.
+.sp
+Default value: \fB1000\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_multihost_import_intervals\fR (uint)
+.ad
+.RS 12n
+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
+.sp
+Default value: \fB10\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_multihost_fail_intervals\fR (uint)
+.ad
+.RS 12n
+Controls the behavior of the pool when multihost write failures 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.
+.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.
+.sp
+Default value: \fB5\fR.
+.RE
+
+.sp
+.ne 2
+.na
 \fBzfs_no_scrub_io\fR (int)
 .ad
 .RS 12n
@@ -1529,8 +1602,8 @@ Default value: \fB1,048,576\fR.
 \fBzfs_read_history\fR (int)
 .ad
 .RS 12n
-Historic statistics for the last N reads will be available in
-\fR/proc/spl/kstat/zfs/POOLNAME/reads\fB
+Historical statistics for the last N reads will be available in
+\fB/proc/spl/kstat/zfs/<pool>/reads\fR
 .sp
 Default value: \fB0\fR (no data is kept).
 .RE
@@ -1684,8 +1757,8 @@ Default value: \fB32\fR.
 \fBzfs_txg_history\fR (int)
 .ad
 .RS 12n
-Historic statistics for the last N txgs will be available in
-\fR/proc/spl/kstat/zfs/POOLNAME/txgs\fB
+Historical statistics for the last N txgs will be available in
+\fB/proc/spl/kstat/zfs/<pool>/txgs\fR
 .sp
 Default value: \fB0\fR.
 .RE
diff --git a/man/man8/zpool.8 b/man/man8/zpool.8
index ea25da300..69d77e961 100644
--- a/man/man8/zpool.8
+++ b/man/man8/zpool.8
@@ -717,6 +717,25 @@ The default value is
 .Sy off .
 This property can also be referred to by its shortened name,
 .Sy listsnaps .
+.It Sy multihost Ns = Ns Sy on Ns | Ns Sy off
+Controls whether a pool activity check should be performed during
+.Nm zpool Cm import .
+When a pool is determined to be active it cannot be imported, even with the
+.Fl f
+option.  This property is intended to be used in failover configurations
+where multiple hosts have access to a pool on shared storage.  When this
+property is on, periodic writes to storage occur to show the pool is in use.
+See
+.Sy zfs_multihost_interval
+in the
+.Xr zfs-module-parameters 5
+man page.  In order to enable this property each host must set a unique hostid.
+See
+.Xr genhostid 1
+and
+.Xr spl-module-paramters 5
+for additional details.  The default value is
+.Sy off .
 .It Sy version Ns = Ns Ar version
 The current on-disk version of the pool.
 This can be increased, but never decreased.
@@ -2335,7 +2354,7 @@ is not set, it is assumed that the user is allowed to run
 .Sh INTERFACE STABILITY
 .Sy Evolving
 .Sh SEE ALSO
-.Xr zed 8
+.Xr zed 8 ,
 .Xr zfs 8 ,
 .Xr zfs-events 5 ,
 .Xr zfs-module-parameters 5 ,