Migrate ZFS-* message descriptions (#49)

Prerequisite for changing the URLs in the command outputs from
zfsonlinux.org to openzfs.github.io/openzfs-docs/

Signed-off-by: Ryan Moeller <ryan@iXsystems.com>

docs/msg/ZFS-8000-HC/index.rst

@@ -0,0 +1,85 @@
+..
+   CDDL HEADER START
+
+   The contents of this file are subject to the terms of the
+   Common Development and Distribution License (the "License").
+   You may not use this file except in compliance with the License.
+
+   You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+   or http://www.opensolaris.org/os/licensing.
+   See the License for the specific language governing permissions
+   and limitations under the License.
+
+   When distributing Covered Code, include this CDDL HEADER in each
+   file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+   If applicable, add the following below this CDDL HEADER, with the
+   fields enclosed by brackets "[]" replaced with your own identifying
+   information: Portions Copyright [yyyy] [name of copyright owner]
+
+   CDDL HEADER END
+
+   Portions Copyright 2007 Sun Microsystems, Inc.
+
+.. highlight:: none
+
+Message ID: ZFS-8000-HC
+=======================
+
+ZFS pool I/O failures
+---------------------
+
++-------------------------+-----------------------------------------+
+| **Type:**               | Error                                   |
++-------------------------+-----------------------------------------+
+| **Severity:**           | Major                                   |
++-------------------------+-----------------------------------------+
+| **Description:**        | The ZFS pool has experienced currently  |
+|                         | unrecoverable I/O failures.             |
++-------------------------+-----------------------------------------+
+| **Automated Response:** | No automated response will be taken.    |
++-------------------------+-----------------------------------------+
+| **Impact:**             | Read and write I/Os cannot be serviced. |
++-------------------------+-----------------------------------------+
+
+.. rubric:: Suggested Action for System Administrator
+
+The pool has experienced I/O failures.  Since the ZFS pool property
+``failmode`` is set to 'wait', all I/Os (reads and writes) are blocked.
+See the zpoolprops(8) manpage for more information on the ``failmode``
+property.  Manual intervention is required for I/Os to be serviced.
+
+You can see which devices are affected by running ``zpool status -x``:
+
+::
+
+   # zpool status -x
+     pool: test
+    state: FAULTED
+   status: There are I/O failures.
+   action: Make sure the affected devices are connected, then run 'zpool clear'.
+      see: https://openzfs.github.io/openzfs-docs/msg/ZFS-8000-HC
+    scrub: none requested
+   config:
+
+           NAME        STATE     READ WRITE CKSUM
+           test        FAULTED      0    13     0  insufficient replicas
+             c0t0d0    FAULTED      0     7     0  experienced I/O failures
+             c0t1d0    ONLINE       0     0     0
+
+   errors: 1 data errors, use '-v' for a list
+
+After you have made sure the affected devices are connected, run ``zpool
+clear`` to allow I/O to the pool again:
+
+::
+
+   # zpool clear test
+
+If I/O failures continue to happen, then applications and commands for the pool
+may hang.  At this point, a reboot may be necessary to allow I/O to the pool
+again.
+
+.. rubric:: Details
+
+The Message ID: ``ZFS-8000-HC`` indicates that the pool has experienced I/O
+failures.  Take the documented action to resolve the problem.