Add automatic hot spare functionality

When a vdev starts getting I/O or checksum errors it is now
possible to automatically rebuild to a hot spare device.

To cleanly support this functionality in a shell script some
additional information was added to all zevent ereports which
include a vdev.  This covers both io and checksum zevents but
may be used but other scripts.

In the Illumos FMA solution the same information is required
but it is retrieved through the libzfs library interface.
Specifically the following members were added:

  vdev_spare_paths  - List of vdev paths for all hot spares.
  vdev_spare_guids  - List of vdev guids for all hot spares.
  vdev_read_errors  - Read errors for the problematic vdev
  vdev_write_errors - Write errors for the problematic vdev
  vdev_cksum_errors - Checksum errors for the problematic vdev.

By default the required hot spare scripts are installed but this
functionality is disabled.  To enable hot sparing uncomment the
ZED_SPARE_ON_IO_ERRORS and ZED_SPARE_ON_CHECKSUM_ERRORS in the
/etc/zfs/zed.d/zed.rc configuration file.

These scripts do no add support for the autoexpand property. At
a minimum this requires adding a new udev rule to detect when
a new device is added to the system.  It also requires that the
autoexpand policy be ported from Illumos, see:

  https://github.com/illumos/illumos-gate/blob/master/usr/src/cmd/syseventd/modules/zfs_mod/zfs_mod.c

Support for detecting the correct name of a vdev when it's not
a whole disk was added by Turbo Fredriksson.

Signed-off-by: Brian Behlendorf <[email protected]>
Signed-off-by: Chris Dunlap <[email protected]>
Signed-off-by: Turbo Fredriksson <[email protected]>
Issue #2

4 files changed, 136 insertions, 0 deletions

diff --git a/cmd/zed/Makefile.am b/cmd/zed/Makefile.am
index 8e4efe919..f1404dea1 100644
--- a/cmd/zed/Makefile.am
+++ b/cmd/zed/Makefile.am
@@ -39,17 +39,21 @@ dist_zedexec_SCRIPTS = \
 	$(top_srcdir)/cmd/zed/zed.d/all-debug.sh \
 	$(top_srcdir)/cmd/zed/zed.d/all-syslog.sh \
 	$(top_srcdir)/cmd/zed/zed.d/checksum-email.sh \
+	$(top_srcdir)/cmd/zed/zed.d/checksum-spare.sh \
 	$(top_srcdir)/cmd/zed/zed.d/data-email.sh \
 	$(top_srcdir)/cmd/zed/zed.d/generic-email.sh \
 	$(top_srcdir)/cmd/zed/zed.d/io-email.sh \
+	$(top_srcdir)/cmd/zed/zed.d/io-spare.sh \
 	$(top_srcdir)/cmd/zed/zed.d/resilver.finish-email.sh \
 	$(top_srcdir)/cmd/zed/zed.d/scrub.finish-email.sh
 
 zedconfdefaults = \
 	all-syslog.sh \
 	checksum-email.sh \
+	checksum-spare.sh \
 	data-email.sh \
 	io-email.sh \
+	io-spare.sh \
 	resilver.finish-email.sh \
 	scrub.finish-email.sh
 
diff --git a/cmd/zed/zed.d/checksum-spare.sh b/cmd/zed/zed.d/checksum-spare.sh
new file mode 120000
index 000000000..f564f9322
--- /dev/null
+++ b/cmd/zed/zed.d/checksum-spare.sh
@@ -0,0 +1 @@
+io-spare.sh
\ No newline at end of file
diff --git a/cmd/zed/zed.d/io-spare.sh b/cmd/zed/zed.d/io-spare.sh
new file mode 100755
index 000000000..dd5bf4e0f
--- /dev/null
+++ b/cmd/zed/zed.d/io-spare.sh
@@ -0,0 +1,125 @@
+#!/bin/sh
+#
+# Replace a device with a hot spare in response to IO or checksum errors.
+# The following actions will be performed automatically when the number
+# of errors exceed the limit set by ZED_SPARE_ON_IO_ERRORS or
+# ZED_SPARE_ON_CHECKSUM_ERRORS.
+#
+# 1) FAULT the device on IO errors, no futher IO will be attempted.
+#    DEGRADE the device on checksum errors, the device is still
+#    functional and can be used to service IO requests.
+# 2) Set the SES fault beacon for the device.
+# 3) Replace the device with a hot spare if any are available.
+#
+# Once the hot sparing operation is complete either the failed device or
+# the hot spare must be manually retired using the 'zpool detach' command.
+# The 'autoreplace' functionality which would normally take care of this
+# under Illumos has not yet been implemented.
+#
+# Full support for autoreplace is planned, but it requires that the full
+# ZFS Diagnosis Engine be ported.  In the meanwhile this script provides
+# the majority of the expected hot spare functionality.
+#
+# Exit codes:
+#  0: replaced by hot spare
+#  1: no hot spare device available
+#  2: hot sparing disabled
+#  3: already faulted or degraded
+#  4: unsupported event class
+#  5: internal error
+#
+test -f "${ZED_SCRIPT_DIR}/zed.rc" && . "${ZED_SCRIPT_DIR}/zed.rc"
+
+test -n "${ZEVENT_POOL}" || exit 5
+test -n "${ZEVENT_SUBCLASS}" || exit 5
+test -n "${ZEVENT_VDEV_PATH}" || exit 5
+test -n "${ZEVENT_VDEV_GUID}" || exit 5
+
+# Defaults to disabled, enable in the zed.rc file.
+ZED_SPARE_ON_IO_ERRORS=${ZED_SPARE_ON_IO_ERRORS:-0}
+ZED_SPARE_ON_CHECKSUM_ERRORS=${ZED_SPARE_ON_CHECKSUM_ERRORS:-0}
+
+if [ ${ZED_SPARE_ON_IO_ERRORS} -eq 0 -a \
+     ${ZED_SPARE_ON_CHECKSUM_ERRORS} -eq 0 ]; then
+	exit 2
+fi
+
+# A lock file is used to serialize execution.
+ZED_LOCKDIR=${ZED_LOCKDIR:-/var/lock}
+LOCKFILE="${ZED_LOCKDIR}/zed.spare.lock"
+
+exec 8> "${LOCKFILE}"
+flock -x 8
+
+# Given a <pool> and <device> return the status, (ONLINE, FAULTED, etc...).
+vdev_status() {
+	local POOL=$1
+	local VDEV=`basename $2`
+
+	${ZPOOL} status ${POOL} | \
+	    awk -v pat="${VDEV}|${VDEV/-part?}" '$0 ~ pat { print $1" "$2 }'
+	return 0
+}
+
+# Fault devices after N I/O errors.
+if [ "${ZEVENT_CLASS}" = "ereport.fs.zfs.io" ]; then
+	ERRORS=`expr ${ZEVENT_VDEV_READ_ERRORS} + ${ZEVENT_VDEV_WRITE_ERRORS}`
+
+	if [ ${ZED_SPARE_ON_IO_ERRORS} -gt 0 -a \
+	     ${ERRORS} -ge ${ZED_SPARE_ON_IO_ERRORS} ]; then
+		ACTION="fault"
+	fi
+# Degrade devices after N checksum errors.
+elif [ "${ZEVENT_CLASS}" = "ereport.fs.zfs.checksum" ]; then
+	ERRORS=${ZEVENT_VDEV_CKSUM_ERRORS}
+
+	if [ ${ZED_SPARE_ON_CHECKSUM_ERRORS} -gt 0 -a \
+	     ${ERRORS} -ge ${ZED_SPARE_ON_CHECKSUM_ERRORS} ]; then
+		ACTION="degrade"
+	fi
+else
+	ACTION=
+fi
+
+if [ -n "${ACTION}" ]; then
+
+	# Device is already FAULTED or DEGRADED
+	set -- `vdev_status ${ZEVENT_POOL} ${ZEVENT_VDEV_PATH}`
+	ZEVENT_VDEV_PATH_FOUND=$1
+	STATUS=$2
+	if [ "${STATUS}" = "FAULTED" -o "${STATUS}" = "DEGRADED" ]; then
+		exit 3
+	fi
+
+	# Step 1) FAULT or DEGRADE the device
+	#
+	${ZINJECT} -d ${ZEVENT_VDEV_GUID} -A ${ACTION} ${ZEVENT_POOL}
+
+	# Step 2) Set the SES fault beacon.
+	#
+	# XXX: Set the 'fault' or 'ident' beacon for the device.  This can
+	# be done through the sg_ses utility, the only hard part is to map
+	# the sd device to its corresponding enclosure and slot.  We may
+	# be able to leverage the existing vdev_id scripts for this.
+	#
+	# $ sg_ses --dev-slot-num=0 --set=ident /dev/sg3
+	# $ sg_ses --dev-slot-num=0 --clear=ident /dev/sg3
+
+	# Step 3) Replace the device with a hot spare.
+	#
+	# Round robin through the spares selecting those which are available.
+	#
+	for SPARE in ${ZEVENT_VDEV_SPARE_PATHS}; do
+		set -- `vdev_status ${ZEVENT_POOL} ${SPARE}`
+		SPARE_VDEV_FOUND=$1
+		STATUS=$2
+		if [ "${STATUS}" = "AVAIL" ]; then
+			${ZPOOL} replace ${ZEVENT_POOL} \
+			    ${ZEVENT_VDEV_GUID} ${SPARE_VDEV_FOUND} && exit 0
+		fi
+	done
+
+	exit 1
+fi
+
+exit 4
diff --git a/cmd/zed/zed.d/zed.rc b/cmd/zed/zed.d/zed.rc
index 57c969c89..69989f953 100644
--- a/cmd/zed/zed.d/zed.rc
+++ b/cmd/zed/zed.d/zed.rc
@@ -26,3 +26,9 @@
 
 # The syslog tag for marking zed events.
 #ZED_SYSLOG_TAG="zed"
+
+# Replace a device with a hot spare after N I/O errors are detected.
+#ZED_SPARE_ON_IO_ERRORS=1
+
+# Replace a device with a hot spare after N checksum errors are detected.
+#ZED_SPARE_ON_CHECKSUM_ERRORS=10