Add information about the -o option to zpool replace

Users need to be aware that when replacing devices in an existing
pool they may need to override automatically detected ashift value.
This will all depend on the exact hardware they are using.

Signed-off-by: Turbo Fredriksson <turbo@bayour.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2024

cmd/zpool/zpool_main.c

@@ -248,8 +248,8 @@ get_usage(zpool_help_t idx) {
 	case HELP_ONLINE:
 		return (gettext("\tonline <pool> <device> ...\n"));
 	case HELP_REPLACE:
-		return (gettext("\treplace [-f] <pool> <device> "
-		    "[new-device]\n"));
+		return (gettext("\treplace [-f] [-o property=value] "
+		    "<pool> <device> [new-device]\n"));
 	case HELP_REMOVE:
 		return (gettext("\tremove <pool> <device> ...\n"));
 	case HELP_REOPEN:

man/man8/zpool.8

@@ -130,7 +130,7 @@ zpool \- configures ZFS storage pools
 
 .LP
 .nf
-\fBzpool replace\fR [\fB-f\fR] \fIpool\fR \fIdevice\fR [\fInew_device\fR]
+\fBzpool replace\fR [\fB-f\fR] [\fB-o\fR \fIproperty=value\fR]  \fIpool\fR \fIdevice\fR [\fInew_device\fR]
 .fi
 
 .LP
@@ -1676,7 +1676,7 @@ Removes the specified device from the pool. This command currently only supports
 .ne 2
 .mk
 .na
-\fB\fBzpool replace\fR [\fB-f\fR] \fIpool\fR \fIold_device\fR [\fInew_device\fR]\fR
+\fB\fBzpool replace\fR [\fB-f\fR] [\fB-o\fR \fIproperty=value\fR] \fIpool\fR \fIold_device\fR [\fInew_device\fR]\fR
 .ad
 .sp .6
 .RS 4n
@@ -1696,6 +1696,17 @@ The size of \fInew_device\fR must be greater than or equal to the minimum size o
 Forces use of \fInew_device\fR, even if its appears to be in use. Not all devices can be overridden in this manner.
 .RE
 
+.sp
+.ne 2
+.mk
+.na
+\fB\fB-o\fR \fIproperty=value\fR
+.ad
+.sp .6n
+.RS 6n
+Sets the given pool properties. See the "Properties" section for a list of valid properties that can be set. The only property supported at the moment is \fBashift\fR.  \fBDo note\fR that some properties (among them \fBashift\fR) are \fInot\fR inherited from a previous vdev. They are vdev specific, not pool specific.
+.RE
+
 .RE
 
 .sp