--- a/usr/src/common/zfs/zfeature_common.c	Fri Aug 23 11:13:02 2013 -0400
+++ b/usr/src/common/zfs/zfeature_common.c	Thu Aug 22 19:03:54 2013 +0000
@@ -22,6 +22,7 @@
 /*
  * Copyright (c) 2012 by Delphix. All rights reserved.
  * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
+ * Copyright (c) 2013, Joyent, Inc. All rights reserved.
  */
 
 #ifdef _KERNEL
@@ -160,4 +161,7 @@
 	zfeature_register(SPA_FEATURE_LZ4_COMPRESS,
 	    "org.illumos:lz4_compress", "lz4_compress",
 	    "LZ4 compression algorithm support.", B_FALSE, B_FALSE, NULL);
+	zfeature_register(SPA_FEATURE_MULTI_VDEV_CRASH_DUMP,
+	    "com.joyent:multi_vdev_crash_dump", "multi_vdev_crash_dump",
+	    "Crash dumps to multiple vdev pools.", B_FALSE, B_FALSE, NULL);
 }

--- a/usr/src/common/zfs/zfeature_common.h	Fri Aug 23 11:13:02 2013 -0400
+++ b/usr/src/common/zfs/zfeature_common.h	Thu Aug 22 19:03:54 2013 +0000
@@ -22,6 +22,7 @@
 /*
  * Copyright (c) 2012 by Delphix. All rights reserved.
  * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
+ * Copyright (c) 2013, Joyent, Inc. All rights reserved.
  */
 
 #ifndef _ZFEATURE_COMMON_H
@@ -54,6 +55,7 @@
 	SPA_FEATURE_ASYNC_DESTROY,
 	SPA_FEATURE_EMPTY_BPOBJ,
 	SPA_FEATURE_LZ4_COMPRESS,
+	SPA_FEATURE_MULTI_VDEV_CRASH_DUMP,
 	SPA_FEATURES
 } spa_feature_t;
 

--- a/usr/src/common/zfs/zfs_prop.c	Fri Aug 23 11:13:02 2013 -0400
+++ b/usr/src/common/zfs/zfs_prop.c	Thu Aug 22 19:03:54 2013 +0000
@@ -22,6 +22,7 @@
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2012 by Delphix. All rights reserved.
  * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
+ * Copyright (c) 2013, Joyent, Inc. All rights reserved.
  */
 
 /* Portions Copyright 2010 Robert Milkowski */
@@ -69,6 +70,7 @@
 		{ "fletcher2",	ZIO_CHECKSUM_FLETCHER_2 },
 		{ "fletcher4",	ZIO_CHECKSUM_FLETCHER_4 },
 		{ "sha256",	ZIO_CHECKSUM_SHA256 },
+		{ "noparity",	ZIO_CHECKSUM_NOPARITY },
 		{ NULL }
 	};
 

--- a/usr/src/lib/libzfs/common/libzfs_pool.c	Fri Aug 23 11:13:02 2013 -0400
+++ b/usr/src/lib/libzfs/common/libzfs_pool.c	Thu Aug 22 19:03:54 2013 +0000
@@ -23,6 +23,7 @@
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright 2011 Nexenta Systems, Inc. All rights reserved.
  * Copyright (c) 2012 by Delphix. All rights reserved.
+ * Copyright (c) 2013, Joyent, Inc. All rights reserved.
  */
 
 #include <ctype.h>
@@ -3958,9 +3959,7 @@
 	uint_t children, c;
 
 	verify(nvlist_lookup_string(config, ZPOOL_CONFIG_TYPE, &type) == 0);
-	if (strcmp(type, VDEV_TYPE_RAIDZ) == 0 ||
-	    strcmp(type, VDEV_TYPE_FILE) == 0 ||
-	    strcmp(type, VDEV_TYPE_LOG) == 0 ||
+	if (strcmp(type, VDEV_TYPE_FILE) == 0 ||
 	    strcmp(type, VDEV_TYPE_HOLE) == 0 ||
 	    strcmp(type, VDEV_TYPE_MISSING) == 0) {
 		zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
@@ -3979,8 +3978,12 @@
 }
 
 /*
- * check if this zvol is allowable for use as a dump device; zero if
- * it is, > 0 if it isn't, < 0 if it isn't a zvol
+ * Check if this zvol is allowable for use as a dump device; zero if
+ * it is, > 0 if it isn't, < 0 if it isn't a zvol.
+ *
+ * Allowable storage configurations include mirrors, all raidz variants, and
+ * pools with log, cache, and spare devices.  Pools which are backed by files or
+ * have missing/hole vdevs are not suitable.
  */
 int
 zvol_check_dump_config(char *arg)
@@ -4042,12 +4045,6 @@
 
 	verify(nvlist_lookup_nvlist_array(nvroot, ZPOOL_CONFIG_CHILDREN,
 	    &top, &toplevels) == 0);
-	if (toplevels != 1) {
-		zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
-		    "'%s' has multiple top level vdevs"), poolname);
-		(void) zfs_error(hdl, EZFS_DEVOVERFLOW, errbuf);
-		goto out;
-	}
 
 	if (!supported_dump_vdev_type(hdl, top[0], errbuf)) {
 		goto out;

--- a/usr/src/man/man1m/zfs.1m	Fri Aug 23 11:13:02 2013 -0400
+++ b/usr/src/man/man1m/zfs.1m	Thu Aug 22 19:03:54 2013 +0000
@@ -23,9 +23,9 @@
 .\" Copyright (c) 2009 Sun Microsystems, Inc. All Rights Reserved.
 .\" Copyright 2011 Joshua M. Clulow <josh@sysmgr.org>
 .\" Copyright (c) 2012 by Delphix. All rights reserved.
-.\" Copyright (c) 2012, Joyent, Inc. All rights reserved.
 .\" Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
 .\" Copyright 2013 Nexenta Systems, Inc.  All Rights Reserved.
+.\" Copyright (c) 2013, Joyent, Inc. All rights reserved.
 .\"
 .TH ZFS 1M "Jan 26, 2013"
 .SH NAME
@@ -106,7 +106,7 @@
 
 .LP
 .nf
-\fBzfs\fR \fBget\fR [\fB-r\fR|\fB-d\fR \fIdepth\fR][\fB-Hp\fR][\fB-o\fR \fIfield\fR[,\fIfield\fR]...] [\fB-t\fR \fItype\fR[,\fItype\fR]...] 
+\fBzfs\fR \fBget\fR [\fB-r\fR|\fB-d\fR \fIdepth\fR][\fB-Hp\fR][\fB-o\fR \fIfield\fR[,\fIfield\fR]...] [\fB-t\fR \fItype\fR[,\fItype\fR]...]
     [\fB-s\fR \fIsource\fR[,\fIsource\fR]...] \fBall\fR | \fIproperty\fR[,\fIproperty\fR]...
     \fIfilesystem\fR|\fIvolume\fR|\fIsnapshot\fR...
 .fi
@@ -934,15 +934,18 @@
 .ne 2
 .na
 \fB\fBchecksum\fR=\fBon\fR | \fBoff\fR | \fBfletcher2\fR | \fBfletcher4\fR |
-\fBsha256\fR\fR
+\fBsha256\fR | \fBnoparity\fR \fR
 .ad
 .sp .6
 .RS 4n
 Controls the checksum used to verify data integrity. The default value is
 \fBon\fR, which automatically selects an appropriate algorithm (currently,
 \fBfletcher4\fR, but this may change in future releases). The value \fBoff\fR
-disables integrity checking on user data. Disabling checksums is \fBNOT\fR a
-recommended practice.
+disables integrity checking on user data. The value \fBnoparity\fR not only
+disables integrity but also disables maintaining parity for user data.  This
+setting is used internally by a dump device residing on a RAID-Z pool and should
+not be used by any other dataset. Disabling checksums is \fBNOT\fR a recommended
+practice.
 .sp
 Changing this property affects only newly-written data.
 .RE

--- a/usr/src/man/man5/zpool-features.5	Fri Aug 23 11:13:02 2013 -0400
+++ b/usr/src/man/man5/zpool-features.5	Thu Aug 22 19:03:54 2013 +0000
@@ -1,6 +1,7 @@
 '\" te
 .\" Copyright (c) 2012 by Delphix. All rights reserved.
 .\" Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
+.\" Copyright (c) 2013, Joyent, Inc. All rights reserved.
 .\" 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
@@ -231,5 +232,26 @@
 
 .RE
 
+.sp
+.ne 2
+.na
+\fB\fBmulti_vdev_crash_dump\fR\fR
+.ad
+.RS 4n
+.TS
+l l .
+GUID	com.joyent:multi_vdev_crash_dump
+READ\-ONLY COMPATIBLE	no
+DEPENDENCIES	none
+.TE
+
+This feature allows a dump device to be configured with a pool comprised
+of multiple vdevs.  Those vdevs may be arranged in any mirrored or raidz
+configuration.
+
+When the \fBmulti_vdev_crash_dump\fR feature is set to \fBenabled\fR,
+the administrator can use the \fBdumpadm\fR(1M) command to configure a
+dump device on a pool comprised of multiple vdevs.
+
 .SH "SEE ALSO"
 \fBzpool\fR(1M)

--- a/usr/src/uts/common/fs/zfs/dbuf.c	Fri Aug 23 11:13:02 2013 -0400
+++ b/usr/src/uts/common/fs/zfs/dbuf.c	Thu Aug 22 19:03:54 2013 +0000
@@ -23,6 +23,7 @@
  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
  * Copyright (c) 2013 by Delphix. All rights reserved.
  * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
+ * Copyright (c) 2013, Joyent, Inc. All rights reserved.
  */
 
 #include <sys/zfs_context.h>
@@ -2751,7 +2752,8 @@
 		    dr->dt.dl.dr_copies, dr->dt.dl.dr_nopwrite);
 		mutex_exit(&db->db_mtx);
 	} else if (db->db_state == DB_NOFILL) {
-		ASSERT(zp.zp_checksum == ZIO_CHECKSUM_OFF);
+		ASSERT(zp.zp_checksum == ZIO_CHECKSUM_OFF ||
+		    zp.zp_checksum == ZIO_CHECKSUM_NOPARITY);
 		dr->dr_zio = zio_write(zio, os->os_spa, txg,
 		    db->db_blkptr, NULL, db->db.db_size, &zp,
 		    dbuf_write_nofill_ready, dbuf_write_nofill_done, db,

--- a/usr/src/uts/common/fs/zfs/dmu.c	Fri Aug 23 11:13:02 2013 -0400
+++ b/usr/src/uts/common/fs/zfs/dmu.c	Thu Aug 22 19:03:54 2013 +0000
@@ -22,8 +22,8 @@
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2013 by Delphix. All rights reserved.
  */
-
 /* Copyright (c) 2013 by Saso Kiselkov. All rights reserved. */
+/* Copyright (c) 2013, Joyent, Inc. All rights reserved. */
 
 #include <sys/dmu.h>
 #include <sys/dmu_impl.h>
@@ -1597,7 +1597,7 @@
 		 * pipeline.
 		 */
 		compress = ZIO_COMPRESS_OFF;
-		checksum = ZIO_CHECKSUM_OFF;
+		checksum = ZIO_CHECKSUM_NOPARITY;
 	} else {
 		compress = zio_compress_select(dn->dn_compress, compress);
 

--- a/usr/src/uts/common/fs/zfs/sys/vdev_disk.h	Fri Aug 23 11:13:02 2013 -0400
+++ b/usr/src/uts/common/fs/zfs/sys/vdev_disk.h	Thu Aug 22 19:03:54 2013 +0000
@@ -21,13 +21,12 @@
 /*
  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
+ * Copyright (c) 2013 Joyent, Inc. All rights reserved.
  */
 
 #ifndef _SYS_VDEV_DISK_H
 #define	_SYS_VDEV_DISK_H
 
-#pragma ident	"%Z%%M%	%I%	%E% SMI"
-
 #include <sys/vdev.h>
 #ifdef _KERNEL
 #include <sys/buf.h>
@@ -40,14 +39,23 @@
 extern "C" {
 #endif
 
+#ifdef _KERNEL
 typedef struct vdev_disk {
 	ddi_devid_t	vd_devid;
 	char		*vd_minor;
 	ldi_handle_t	vd_lh;
 } vdev_disk_t;
+#endif
 
+extern int vdev_disk_physio(vdev_t *,
+    caddr_t, size_t, uint64_t, int, boolean_t);
+
+/*
+ * Since vdev_disk.c is not compiled into libzpool, this function should only be
+ * defined in the zfs kernel module.
+ */
 #ifdef _KERNEL
-extern int vdev_disk_physio(ldi_handle_t, caddr_t, size_t, uint64_t, int);
+extern int vdev_disk_ldi_physio(ldi_handle_t, caddr_t, size_t, uint64_t, int);
 #endif
 #ifdef	__cplusplus
 }

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/usr/src/uts/common/fs/zfs/sys/vdev_raidz.h	Thu Aug 22 19:03:54 2013 +0000
@@ -0,0 +1,48 @@
+/*
+ * 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
+ */
+/*
+ * Copyright (c) 2013, Joyent, Inc. All rights reserved.
+ */
+
+#ifndef _SYS_VDEV_RAIDZ_H
+#define	_SYS_VDEV_RAIDZ_H
+
+#include <sys/vdev.h>
+#include <sys/semaphore.h>
+#ifdef _KERNEL
+#include <sys/ddi.h>
+#include <sys/sunldi.h>
+#include <sys/sunddi.h>
+#endif
+
+#ifdef	__cplusplus
+extern "C" {
+#endif
+
+#ifdef _KERNEL
+extern int vdev_raidz_physio(vdev_t *,
+    caddr_t, size_t, uint64_t, uint64_t, boolean_t, boolean_t);
+#endif
+#ifdef	__cplusplus
+}
+#endif
+
+#endif	/* _SYS_VDEV_RAIDZ_H */

--- a/usr/src/uts/common/fs/zfs/sys/zio.h	Fri Aug 23 11:13:02 2013 -0400
+++ b/usr/src/uts/common/fs/zfs/sys/zio.h	Thu Aug 22 19:03:54 2013 +0000
@@ -24,6 +24,7 @@
  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
  * Copyright (c) 2012 by Delphix. All rights reserved.
  * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
+ * Copyright (c) 2013, Joyent, Inc. All rights reserved.
  */
 
 #ifndef _ZIO_H
@@ -79,6 +80,7 @@
 	ZIO_CHECKSUM_FLETCHER_4,
 	ZIO_CHECKSUM_SHA256,
 	ZIO_CHECKSUM_ZILOG2,
+	ZIO_CHECKSUM_NOPARITY,
 	ZIO_CHECKSUM_FUNCTIONS
 };
 

--- a/usr/src/uts/common/fs/zfs/vdev_disk.c	Fri Aug 23 11:13:02 2013 -0400
+++ b/usr/src/uts/common/fs/zfs/vdev_disk.c	Thu Aug 22 19:03:54 2013 +0000
@@ -22,6 +22,7 @@
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2013 by Delphix. All rights reserved.
  * Copyright 2013 Nexenta Systems, Inc.  All rights reserved.
+ * Copyright 2013 Joyent, Inc.  All rights reserved.
  */
 
 #include <sys/zfs_context.h>
@@ -426,8 +427,29 @@
 }
 
 int
-vdev_disk_physio(ldi_handle_t vd_lh, caddr_t data, size_t size,
-    uint64_t offset, int flags)
+vdev_disk_physio(vdev_t *vd, caddr_t data,
+    size_t size, uint64_t offset, int flags, boolean_t isdump)
+{
+	vdev_disk_t *dvd = vd->vdev_tsd;
+
+	ASSERT(vd->vdev_ops == &vdev_disk_ops);
+
+	/*
+	 * If in the context of an active crash dump, use the ldi_dump(9F)
+	 * call instead of ldi_strategy(9F) as usual.
+	 */
+	if (isdump) {
+		ASSERT3P(dvd, !=, NULL);
+		return (ldi_dump(dvd->vd_lh, data, lbtodb(offset),
+		    lbtodb(size)));
+	}
+
+	return (vdev_disk_ldi_physio(dvd->vd_lh, data, size, offset, flags));
+}
+
+int
+vdev_disk_ldi_physio(ldi_handle_t vd_lh, caddr_t data,
+    size_t size, uint64_t offset, int flags)
 {
 	buf_t *bp;
 	int error = 0;
@@ -675,7 +697,7 @@
 
 		/* read vdev label */
 		offset = vdev_label_offset(size, l, 0);
-		if (vdev_disk_physio(vd_lh, (caddr_t)label,
+		if (vdev_disk_ldi_physio(vd_lh, (caddr_t)label,
 		    VDEV_SKIP_SIZE + VDEV_PHYS_SIZE, offset, B_READ) != 0)
 			continue;
 

--- a/usr/src/uts/common/fs/zfs/vdev_raidz.c	Fri Aug 23 11:13:02 2013 -0400
+++ b/usr/src/uts/common/fs/zfs/vdev_raidz.c	Thu Aug 22 19:03:54 2013 +0000
@@ -22,11 +22,15 @@
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2013 by Delphix. All rights reserved.
+ * Copyright (c) 2013, Joyent, Inc. All rights reserved.
  */
 
 #include <sys/zfs_context.h>
 #include <sys/spa.h>
 #include <sys/vdev_impl.h>
+#include <sys/vdev_disk.h>
+#include <sys/vdev_file.h>
+#include <sys/vdev_raidz.h>
 #include <sys/zio.h>
 #include <sys/zio_checksum.h>
 #include <sys/fs/zfs.h>
@@ -154,6 +158,8 @@
 	VDEV_RAIDZ_64MUL_2((x), mask); \
 }
 
+#define	VDEV_LABEL_OFFSET(x)	(x + VDEV_LABEL_START_SIZE)
+
 /*
  * Force reconstruction to use the general purpose method.
  */
@@ -435,14 +441,14 @@
  * the number of children in the target vdev.
  */
 static raidz_map_t *
-vdev_raidz_map_alloc(zio_t *zio, uint64_t unit_shift, uint64_t dcols,
-    uint64_t nparity)
+vdev_raidz_map_alloc(caddr_t data, uint64_t size, uint64_t offset,
+    uint64_t unit_shift, uint64_t dcols, uint64_t nparity)
 {
 	raidz_map_t *rm;
 	/* The starting RAIDZ (parent) vdev sector of the block. */
-	uint64_t b = zio->io_offset >> unit_shift;
+	uint64_t b = offset >> unit_shift;
 	/* The zio's size in units of the vdev's minimum sector size. */
-	uint64_t s = zio->io_size >> unit_shift;
+	uint64_t s = size >> unit_shift;
 	/* The first column for this stripe. */
 	uint64_t f = b % dcols;
 	/* The starting byte offset on each child vdev. */
@@ -533,7 +539,7 @@
 	for (c = 0; c < rm->rm_firstdatacol; c++)
 		rm->rm_col[c].rc_data = zio_buf_alloc(rm->rm_col[c].rc_size);
 
-	rm->rm_col[c].rc_data = zio->io_data;
+	rm->rm_col[c].rc_data = data;
 
 	for (c = c + 1; c < acols; c++)
 		rm->rm_col[c].rc_data = (char *)rm->rm_col[c - 1].rc_data +
@@ -562,7 +568,7 @@
 	ASSERT(rm->rm_cols >= 2);
 	ASSERT(rm->rm_col[0].rc_size == rm->rm_col[1].rc_size);
 
-	if (rm->rm_firstdatacol == 1 && (zio->io_offset & (1ULL << 20))) {
+	if (rm->rm_firstdatacol == 1 && (offset & (1ULL << 20))) {
 		devidx = rm->rm_col[0].rc_devidx;
 		o = rm->rm_col[0].rc_offset;
 		rm->rm_col[0].rc_devidx = rm->rm_col[1].rc_devidx;
@@ -574,8 +580,6 @@
 			rm->rm_skipstart = 1;
 	}
 
-	zio->io_vsd = rm;
-	zio->io_vsd_ops = &vdev_raidz_vsd_ops;
 	return (rm);
 }
 
@@ -985,12 +989,9 @@
  *           ~~                               ~~
  *           __                               __
  *           |  1   1   1   1   1   1   1   1  |
- *           | 128  64  32  16  8   4   2   1  |
  *           |  19 205 116  29  64  16  4   1  |
  *           |  1   0   0   0   0   0   0   0  |
- *           |  0   1   0   0   0   0   0   0  |
- *  (V|I)' = |  0   0   1   0   0   0   0   0  |
- *           |  0   0   0   1   0   0   0   0  |
+ *  (V|I)' = |  0   0   0   1   0   0   0   0  |
  *           |  0   0   0   0   1   0   0   0  |
  *           |  0   0   0   0   0   1   0   0  |
  *           |  0   0   0   0   0   0   1   0  |
@@ -1522,6 +1523,152 @@
 		vdev_close(vd->vdev_child[c]);
 }
 
+/*
+ * Handle a read or write I/O to a RAID-Z dump device.
+ *
+ * The dump device is in a unique situation compared to other ZFS datasets:
+ * writing to this device should be as simple and fast as possible.  In
+ * addition, durability matters much less since the dump will be extracted
+ * once the machine reboots.  For that reason, this function eschews parity for
+ * performance and simplicity.  The dump device uses the checksum setting
+ * ZIO_CHECKSUM_NOPARITY to indicate that parity is not maintained for this
+ * dataset.
+ *
+ * Blocks of size 128 KB have been preallocated for this volume.  I/Os less than
+ * 128 KB will not fill an entire block; in addition, they may not be properly
+ * aligned.  In that case, this function uses the preallocated 128 KB block and
+ * omits reading or writing any "empty" portions of that block, as opposed to
+ * allocating a fresh appropriately-sized block.
+ *
+ * Looking at an example of a 32 KB I/O to a RAID-Z vdev with 5 child vdevs:
+ *
+ *     vdev_raidz_io_start(data, size: 32 KB, offset: 64 KB)
+ *
+ * If this were a standard RAID-Z dataset, a block of at least 40 KB would be
+ * allocated which spans all five child vdevs.  8 KB of data would be written to
+ * each of four vdevs, with the fifth containing the parity bits.
+ *
+ *       parity    data     data     data     data
+ *     |   PP   |   XX   |   XX   |   XX   |   XX   |
+ *         ^        ^        ^        ^        ^
+ *         |        |        |        |        |
+ *   8 KB parity    ------8 KB data blocks------
+ *
+ * However, when writing to the dump device, the behavior is different:
+ *
+ *     vdev_raidz_physio(data, size: 32 KB, offset: 64 KB)
+ *
+ * Unlike the normal RAID-Z case in which the block is allocated based on the
+ * I/O size, reads and writes here always use a 128 KB logical I/O size.  If the
+ * I/O size is less than 128 KB, only the actual portions of data are written.
+ * In this example the data is written to the third data vdev since that vdev
+ * contains the offset [64 KB, 96 KB).
+ *
+ *       parity    data     data     data     data
+ *     |        |        |        |   XX   |        |
+ *                                    ^
+ *                                    |
+ *                             32 KB data block
+ *
+ * As a result, an individual I/O may not span all child vdevs; moreover, a
+ * small I/O may only operate on a single child vdev.
+ *
+ * Note that since there are no parity bits calculated or written, this format
+ * remains the same no matter how many parity bits are used in a normal RAID-Z
+ * stripe.  On a RAID-Z3 configuration with seven child vdevs, the example above
+ * would look like:
+ *
+ *       parity   parity   parity    data     data     data     data
+ *     |        |        |        |        |        |   XX   |        |
+ *                                                      ^
+ *                                                      |
+ *                                               32 KB data block
+ */
+int
+vdev_raidz_physio(vdev_t *vd, caddr_t data, size_t size,
+    uint64_t offset, uint64_t origoffset, boolean_t doread, boolean_t isdump)
+{
+	vdev_t *tvd = vd->vdev_top;
+	vdev_t *cvd;
+	raidz_map_t *rm;
+	raidz_col_t *rc;
+	int c, err = 0;
+
+	uint64_t start, end, colstart, colend;
+	uint64_t coloffset, colsize, colskip;
+
+	int flags = doread ? B_READ : B_WRITE;
+
+#ifdef	_KERNEL
+
+	/*
+	 * Don't write past the end of the block
+	 */
+	VERIFY3U(offset + size, <=, origoffset + SPA_MAXBLOCKSIZE);
+
+	start = offset;
+	end = start + size;
+
+	/*
+	 * Allocate a RAID-Z map for this block.  Note that this block starts
+	 * from the "original" offset, this is, the offset of the extent which
+	 * contains the requisite offset of the data being read or written.
+	 *
+	 * Even if this I/O operation doesn't span the full block size, let's
+	 * treat the on-disk format as if the only blocks are the complete 128
+	 * KB size.
+	 */
+	rm = vdev_raidz_map_alloc(data - (offset - origoffset),
+	    SPA_MAXBLOCKSIZE, origoffset, tvd->vdev_ashift, vd->vdev_children,
+	    vd->vdev_nparity);
+
+	coloffset = origoffset;
+
+	for (c = rm->rm_firstdatacol; c < rm->rm_cols;
+	    c++, coloffset += rc->rc_size) {
+		rc = &rm->rm_col[c];
+		cvd = vd->vdev_child[rc->rc_devidx];
+
+		/*
+		 * Find the start and end of this column in the RAID-Z map,
+		 * keeping in mind that the stated size and offset of the
+		 * operation may not fill the entire column for this vdev.
+		 *
+		 * If any portion of the data spans this column, issue the
+		 * appropriate operation to the vdev.
+		 */
+		if (coloffset + rc->rc_size <= start)
+			continue;
+		if (coloffset >= end)
+			continue;
+
+		colstart = MAX(coloffset, start);
+		colend = MIN(end, coloffset + rc->rc_size);
+		colsize = colend - colstart;
+		colskip = colstart - coloffset;
+
+		VERIFY3U(colsize, <=, rc->rc_size);
+		VERIFY3U(colskip, <=, rc->rc_size);
+
+		/*
+		 * Note that the child vdev will have a vdev label at the start
+		 * of its range of offsets, hence the need for
+		 * VDEV_LABEL_OFFSET().  See zio_vdev_child_io() for another
+		 * example of why this calculation is needed.
+		 */
+		if ((err = vdev_disk_physio(cvd,
+		    ((char *)rc->rc_data) + colskip, colsize,
+		    VDEV_LABEL_OFFSET(rc->rc_offset) + colskip,
+		    flags, isdump)) != 0)
+			break;
+	}
+
+	vdev_raidz_map_free(rm);
+#endif	/* KERNEL */
+
+	return (err);
+}
+
 static uint64_t
 vdev_raidz_asize(vdev_t *vd, uint64_t psize)
 {
@@ -1574,9 +1721,13 @@
 	raidz_col_t *rc;
 	int c, i;
 
-	rm = vdev_raidz_map_alloc(zio, tvd->vdev_ashift, vd->vdev_children,
+	rm = vdev_raidz_map_alloc(zio->io_data, zio->io_size, zio->io_offset,
+	    tvd->vdev_ashift, vd->vdev_children,
 	    vd->vdev_nparity);
 
+	zio->io_vsd = rm;
+	zio->io_vsd_ops = &vdev_raidz_vsd_ops;
+
 	ASSERT3U(rm->rm_asize, ==, vdev_psize_to_asize(vd, zio->io_size));
 
 	if (zio->io_type == ZIO_TYPE_WRITE) {
@@ -1707,6 +1858,13 @@
 	int c, ret = 0;
 	raidz_col_t *rc;
 
+	blkptr_t *bp = zio->io_bp;
+	enum zio_checksum checksum = (bp == NULL ? zio->io_prop.zp_checksum :
+	    (BP_IS_GANG(bp) ? ZIO_CHECKSUM_GANG_HEADER : BP_GET_CHECKSUM(bp)));
+
+	if (checksum == ZIO_CHECKSUM_NOPARITY)
+		return (ret);
+
 	for (c = 0; c < rm->rm_firstdatacol; c++) {
 		rc = &rm->rm_col[c];
 		if (!rc->rc_tried || rc->rc_error != 0)

--- a/usr/src/uts/common/fs/zfs/zio_checksum.c	Fri Aug 23 11:13:02 2013 -0400
+++ b/usr/src/uts/common/fs/zfs/zio_checksum.c	Thu Aug 22 19:03:54 2013 +0000
@@ -21,6 +21,7 @@
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2013 by Delphix. All rights reserved.
+ * Copyright (c) 2013, Joyent, Inc. All rights reserved.
  */
 
 #include <sys/zfs_context.h>
@@ -78,6 +79,7 @@
 	{{fletcher_4_native,	fletcher_4_byteswap},	1, 0, 0, "fletcher4"},
 	{{zio_checksum_SHA256,	zio_checksum_SHA256},	1, 0, 1, "sha256"},
 	{{fletcher_4_native,	fletcher_4_byteswap},	0, 1, 0, "zilog2"},
+	{{zio_checksum_off,	zio_checksum_off},	0, 0, 0, "noparity"},
 };
 
 enum zio_checksum

--- a/usr/src/uts/common/fs/zfs/zvol.c	Fri Aug 23 11:13:02 2013 -0400
+++ b/usr/src/uts/common/fs/zfs/zvol.c	Thu Aug 22 19:03:54 2013 +0000
@@ -25,6 +25,7 @@
  *
  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
  * Copyright (c) 2013 by Delphix. All rights reserved.
+ * Copyright (c) 2013, Joyent, Inc. All rights reserved.
  */
 
 /*
@@ -54,6 +55,7 @@
 #include <sys/stat.h>
 #include <sys/zap.h>
 #include <sys/spa.h>
+#include <sys/spa_impl.h>
 #include <sys/zio.h>
 #include <sys/dmu_traverse.h>
 #include <sys/dnode.h>
@@ -77,10 +79,14 @@
 #include <sys/zfs_rlock.h>
 #include <sys/vdev_disk.h>
 #include <sys/vdev_impl.h>
+#include <sys/vdev_raidz.h>
 #include <sys/zvol.h>
 #include <sys/dumphdr.h>
 #include <sys/zil_impl.h>
 #include <sys/dbuf.h>
+#include <sys/dmu_tx.h>
+#include <sys/zfeature.h>
+#include <sys/zio_checksum.h>
 
 #include "zfs_namecheck.h"
 
@@ -1101,27 +1107,28 @@
 }
 
 static int
-zvol_dumpio_vdev(vdev_t *vd, void *addr, uint64_t offset, uint64_t size,
-    boolean_t doread, boolean_t isdump)
+zvol_dumpio_vdev(vdev_t *vd, void *addr, uint64_t offset, uint64_t origoffset,
+    uint64_t size, boolean_t doread, boolean_t isdump)
 {
 	vdev_disk_t *dvd;
 	int c;
 	int numerrors = 0;
 
-	for (c = 0; c < vd->vdev_children; c++) {
-		ASSERT(vd->vdev_ops == &vdev_mirror_ops ||
-		    vd->vdev_ops == &vdev_replacing_ops ||
-		    vd->vdev_ops == &vdev_spare_ops);
-		int err = zvol_dumpio_vdev(vd->vdev_child[c],
-		    addr, offset, size, doread, isdump);
-		if (err != 0) {
-			numerrors++;
-		} else if (doread) {
-			break;
+	if (vd->vdev_ops == &vdev_mirror_ops ||
+	    vd->vdev_ops == &vdev_replacing_ops ||
+	    vd->vdev_ops == &vdev_spare_ops) {
+		for (c = 0; c < vd->vdev_children; c++) {
+			int err = zvol_dumpio_vdev(vd->vdev_child[c],
+			    addr, offset, origoffset, size, doread, isdump);
+			if (err != 0) {
+				numerrors++;
+			} else if (doread) {
+				break;
+			}
 		}
 	}
 
-	if (!vd->vdev_ops->vdev_op_leaf)
+	if (!vd->vdev_ops->vdev_op_leaf && vd->vdev_ops != &vdev_raidz_ops)
 		return (numerrors < vd->vdev_children ? 0 : EIO);
 
 	if (doread && !vdev_readable(vd))
@@ -1129,19 +1136,26 @@
 	else if (!doread && !vdev_writeable(vd))
 		return (SET_ERROR(EIO));
 
-	dvd = vd->vdev_tsd;
-	ASSERT3P(dvd, !=, NULL);
+	if (vd->vdev_ops == &vdev_raidz_ops) {
+		return (vdev_raidz_physio(vd,
+		    addr, size, offset, origoffset, doread, isdump));
+	}
+
 	offset += VDEV_LABEL_START_SIZE;
 
 	if (ddi_in_panic() || isdump) {
 		ASSERT(!doread);
 		if (doread)
 			return (SET_ERROR(EIO));
+		dvd = vd->vdev_tsd;
+		ASSERT3P(dvd, !=, NULL);
 		return (ldi_dump(dvd->vd_lh, addr, lbtodb(offset),
 		    lbtodb(size)));
 	} else {
-		return (vdev_disk_physio(dvd->vd_lh, addr, size, offset,
-		    doread ? B_READ : B_WRITE));
+		dvd = vd->vdev_tsd;
+		ASSERT3P(dvd, !=, NULL);
+		return (vdev_disk_ldi_physio(dvd->vd_lh, addr, size,
+		    offset, doread ? B_READ : B_WRITE));
 	}
 }
 
@@ -1176,7 +1190,8 @@
 
 	vd = vdev_lookup_top(spa, DVA_GET_VDEV(&ze->ze_dva));
 	offset += DVA_GET_OFFSET(&ze->ze_dva);
-	error = zvol_dumpio_vdev(vd, addr, offset, size, doread, isdump);
+	error = zvol_dumpio_vdev(vd, addr, offset, DVA_GET_OFFSET(&ze->ze_dva),
+	    size, doread, isdump);
 
 	if (!ddi_in_panic())
 		spa_config_exit(spa, SCL_STATE, FTAG);
@@ -1196,7 +1211,7 @@
 	rl_t *rl;
 	int error = 0;
 	boolean_t doread = bp->b_flags & B_READ;
-	boolean_t is_dump;
+	boolean_t is_dumpified;
 	boolean_t sync;
 
 	if (getminor(bp->b_edev) == 0) {
@@ -1239,11 +1254,11 @@
 		return (0);
 	}
 
-	is_dump = zv->zv_flags & ZVOL_DUMPIFIED;
+	is_dumpified = zv->zv_flags & ZVOL_DUMPIFIED;
 	sync = ((!(bp->b_flags & B_ASYNC) &&
 	    !(zv->zv_flags & ZVOL_WCE)) ||
 	    (zv->zv_objset->os_sync == ZFS_SYNC_ALWAYS)) &&
-	    !doread && !is_dump;
+	    !doread && !is_dumpified;
 
 	/*
 	 * There must be no buffer changes when doing a dmu_sync() because
@@ -1254,7 +1269,7 @@
 
 	while (resid != 0 && off < volsize) {
 		size_t size = MIN(resid, zvol_maxphys);
-		if (is_dump) {
+		if (is_dumpified) {
 			size = MIN(size, P2END(off, zv->zv_volblocksize) - off);
 			error = zvol_dumpio(zv, addr, off, size,
 			    doread, B_FALSE);
@@ -1813,21 +1828,67 @@
 	ddi_soft_state_fini(&zfsdev_state);
 }
 
+/*ARGSUSED*/
+static int
+zfs_mvdev_dump_feature_check(void *arg, dmu_tx_t *tx)
+{
+	spa_t *spa = dmu_tx_pool(tx)->dp_spa;
+
+	if (spa_feature_is_active(spa,
+	    &spa_feature_table[SPA_FEATURE_MULTI_VDEV_CRASH_DUMP]))
+		return (1);
+	return (0);
+}
+
+/*ARGSUSED*/
+static void
+zfs_mvdev_dump_activate_feature_sync(void *arg, dmu_tx_t *tx)
+{
+	spa_t *spa = dmu_tx_pool(tx)->dp_spa;
+
+	spa_feature_incr(spa,
+	    &spa_feature_table[SPA_FEATURE_MULTI_VDEV_CRASH_DUMP], tx);
+}
+
 static int
 zvol_dump_init(zvol_state_t *zv, boolean_t resize)
 {
 	dmu_tx_t *tx;
-	int error = 0;
+	int error;
 	objset_t *os = zv->zv_objset;
+	spa_t *spa = dmu_objset_spa(os);
+	vdev_t *vd = spa->spa_root_vdev;
 	nvlist_t *nv = NULL;
-	uint64_t version = spa_version(dmu_objset_spa(zv->zv_objset));
+	uint64_t version = spa_version(spa);
+	enum zio_checksum checksum;
 
 	ASSERT(MUTEX_HELD(&zfsdev_state_lock));
+	ASSERT(vd->vdev_ops == &vdev_root_ops);
+
 	error = dmu_free_long_range(zv->zv_objset, ZVOL_OBJ, 0,
 	    DMU_OBJECT_END);
 	/* wait for dmu_free_long_range to actually free the blocks */
 	txg_wait_synced(dmu_objset_pool(zv->zv_objset), 0);
 
+	/*
+	 * If the pool on which the dump device is being initialized has more
+	 * than one child vdev, check that the MULTI_VDEV_CRASH_DUMP feature is
+	 * enabled.  If so, bump that feature's counter to indicate that the
+	 * feature is active. We also check the vdev type to handle the
+	 * following case:
+	 *   # zpool create test raidz disk1 disk2 disk3
+	 *   Now have spa_root_vdev->vdev_children == 1 (the raidz vdev),
+	 *   the raidz vdev itself has 3 children.
+	 */
+	if (vd->vdev_children > 1 || vd->vdev_ops == &vdev_raidz_ops) {
+		if (!spa_feature_is_enabled(spa,
+		    &spa_feature_table[SPA_FEATURE_MULTI_VDEV_CRASH_DUMP]))
+			return (SET_ERROR(ENOTSUP));
+		(void) dsl_sync_task(spa_name(spa),
+		    zfs_mvdev_dump_feature_check,
+		    zfs_mvdev_dump_activate_feature_sync, NULL, 2);
+	}
+
 	tx = dmu_tx_create(os);
 	dmu_tx_hold_zap(tx, ZVOL_ZAP_OBJ, TRUE, NULL);
 	dmu_tx_hold_bonus(tx, ZVOL_OBJ);
@@ -1838,6 +1899,14 @@
 	}
 
 	/*
+	 * If MULTI_VDEV_CRASH_DUMP is active, use the NOPARITY checksum
+	 * function.  Otherwise, use the old default -- OFF.
+	 */
+	checksum = spa_feature_is_active(spa,
+	    &spa_feature_table[SPA_FEATURE_MULTI_VDEV_CRASH_DUMP]) ?
+	    ZIO_CHECKSUM_NOPARITY : ZIO_CHECKSUM_OFF;
+
+	/*
 	 * If we are resizing the dump device then we only need to
 	 * update the refreservation to match the newly updated
 	 * zvolsize. Otherwise, we save off the original state of the
@@ -1900,7 +1969,7 @@
 		    ZIO_COMPRESS_OFF) == 0);
 		VERIFY(nvlist_add_uint64(nv,
 		    zfs_prop_to_name(ZFS_PROP_CHECKSUM),
-		    ZIO_CHECKSUM_OFF) == 0);
+		    checksum) == 0);
 		if (version >= SPA_VERSION_DEDUP) {
 			VERIFY(nvlist_add_uint64(nv,
 			    zfs_prop_to_name(ZFS_PROP_DEDUP),