diff --git a/man/man5/zfs-module-parameters.5 b/man/man5/zfs-module-parameters.5
index 586712940a87..d3aa2e6b043b 100644
--- a/man/man5/zfs-module-parameters.5
+++ b/man/man5/zfs-module-parameters.5
@@ -729,6 +729,32 @@ Disable meta data compression
 Use \fB1\fR for yes and \fB0\fR for no (default).
 .RE
 
+.sp
+.ne 2
+.na
+\fBzfs_mg_noalloc_threshold\fR (int)
+.ad
+.RS 12n
+Defines a threshold at which metaslab groups should be eligible for
+allocations.  The value is expressed as a percentage of free space
+beyond which a metaslab group is always eligible for allocations.
+If a metaslab group's free space is less than or equal to the
+the threshold, the allocator will avoid allocating to that group
+unless all groups in the pool have reached the threshold.  Once all
+groups have reached the threshold, all groups are allowed to accept
+allocations.  The default value of 0 disables the feature and causes
+all metaslab groups to be eligible for allocations.
+
+This parameter allows to deal with pools having heavily imbalanced
+vdevs such as would be the case when a new vdev has been added.
+Setting the threshold to a non-zero percentage will stop allocations
+from being made to vdevs that aren't filled to the specified percentage
+and allow lesser filled vdevs to acquire more allocations than they
+otherwise would under the old \fBzfs_mg_alloc_failures\fR facility.
+.sp
+Default value: \fB0\fR.
+.RE
+
 .sp
 .ne 2
 .na
diff --git a/module/zfs/metaslab.c b/module/zfs/metaslab.c
index 6aa5e063f47d..a8b4b0a0e578 100644
--- a/module/zfs/metaslab.c
+++ b/module/zfs/metaslab.c
@@ -2120,4 +2120,8 @@ MODULE_PARM_DESC(metaslab_debug_load, "load all metaslabs during pool import");
 module_param(metaslab_debug_unload, int, 0644);
 MODULE_PARM_DESC(metaslab_debug_unload,
 	"prevent metaslabs from being unloaded");
+
+module_param(zfs_mg_noalloc_threshold, int, 0644);
+MODULE_PARM_DESC(zfs_mg_noalloc_threshold,
+	"percentage of free space for metaslab group to allow allocation");
 #endif /* _KERNEL && HAVE_SPL */