Distributed Spare (dRAID) Feature

This patch adds a new top-level vdev type called dRAID, which stands
for Distributed parity RAID.  This pool configuration allows all dRAID
vdevs to participate when rebuilding to a distributed hot spare device.
This can substantially reduce the total time required to restore full
parity to pool with a failed device.

A dRAID pool can be created using the new top-level `draid` type.
Like `raidz`, the desired redundancy is specified after the type:
`draid[1,2,3]`.  No additional information is required to create the
pool and reasonable default values will be chosen based on the number
of child vdevs in the dRAID vdev.

    zpool create <pool> draid[1,2,3] <vdevs...>

Unlike raidz, additional optional dRAID configuration values can be
provided as part of the draid type as colon separated values. This
allows administrators to fully specify a layout for either performance
or capacity reasons.  The supported options include:

    zpool create <pool> \
        draid[<parity>][:<data>d][:<children>c][:<spares>s] \
        <vdevs...>

    - draid[parity]       - Parity level (default 1)
    - draid[:<data>d]     - Data devices per group (default 8)
    - draid[:<children>c] - Expected number of child vdevs
    - draid[:<spares>s]   - Distributed hot spares (default 0)

Abbreviated example `zpool status` output for a 68 disk dRAID pool
with two distributed spares using special allocation classes.

```
  pool: tank
 state: ONLINE
config:

    NAME                  STATE     READ WRITE CKSUM
    slag7                 ONLINE       0     0     0
      draid2:8d:68c:2s-0  ONLINE       0     0     0
        L0                ONLINE       0     0     0
        L1                ONLINE       0     0     0
        ...
        U25               ONLINE       0     0     0
        U26               ONLINE       0     0     0
        spare-53          ONLINE       0     0     0
          U27             ONLINE       0     0     0
          draid2-0-0      ONLINE       0     0     0
        U28               ONLINE       0     0     0
        U29               ONLINE       0     0     0
        ...
        U42               ONLINE       0     0     0
        U43               ONLINE       0     0     0
    special
      mirror-1            ONLINE       0     0     0
        L5                ONLINE       0     0     0
        U5                ONLINE       0     0     0
      mirror-2            ONLINE       0     0     0
        L6                ONLINE       0     0     0
        U6                ONLINE       0     0     0
    spares
      draid2-0-0          INUSE     currently in use
      draid2-0-1          AVAIL
```

When adding test coverage for the new dRAID vdev type the following
options were added to the ztest command.  These options are leverages
by zloop.sh to test a wide range of dRAID configurations.

    -K draid|raidz|random - kind of RAID to test
    -D <value>            - dRAID data drives per group
    -S <value>            - dRAID distributed hot spares
    -R <value>            - RAID parity (raidz or dRAID)

The zpool_create, zpool_import, redundancy, replacement and fault
test groups have all been updated provide test coverage for the
dRAID feature.

Co-authored-by: Isaac Huang <[email protected]>
Co-authored-by: Mark Maybee <[email protected]>
Co-authored-by: Don Brady <[email protected]>
Co-authored-by: Matthew Ahrens <[email protected]>
Co-authored-by: Brian Behlendorf <[email protected]>
Reviewed-by: Mark Maybee <[email protected]>
Reviewed-by: Matt Ahrens <[email protected]>
Reviewed-by: Tony Hutter <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes #10102 

2 files changed, 49 insertions, 0 deletions

diff --git a/man/man5/zfs-module-parameters.5 b/man/man5/zfs-module-parameters.5
index 469963750..5b4dac42f 100644
--- a/man/man5/zfs-module-parameters.5
+++ b/man/man5/zfs-module-parameters.5
@@ -2905,6 +2905,31 @@ Default value: \fB1,048,576\fR.
 .sp
 .ne 2
 .na
+\fBzfs_rebuild_scrub_enabled\fR (int)
+.ad
+.RS 12n
+Automatically start a pool scrub when the last active sequential resilver
+completes in order to verify the checksums of all blocks which have been
+resilvered. This option is enabled by default and is strongly recommended.
+.sp
+Default value: \fB1\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_rebuild_vdev_limit\fR (ulong)
+.ad
+.RS 12n
+Maximum amount of i/o that can be concurrently issued for a sequential
+resilver per leaf device, given in bytes.
+.sp
+Default value: \fB33,554,432\fR.
+.RE
+
+.sp
+.ne 2
+.na
 \fBzfs_reconstruct_indirect_combinations_max\fR (int)
 .ad
 .RS 12na
diff --git a/man/man5/zpool-features.5 b/man/man5/zpool-features.5
index 08a84ece2..2e5ab4c37 100644
--- a/man/man5/zpool-features.5
+++ b/man/man5/zpool-features.5
@@ -309,6 +309,30 @@ on a top-level vdev, and will never return to being \fBenabled\fR.
 .sp
 .ne 2
 .na
+\fBdraid\fR
+.ad
+.RS 4n
+.TS
+l l .
+GUID	org.openzfs:draid
+READ\-ONLY COMPATIBLE	no
+DEPENDENCIES	none
+.TE
+
+This feature enables use of the \fBdraid\fR vdev type.  dRAID is a variant
+of raidz which provides integrated distributed hot spares that allow faster
+resilvering while retaining the benefits of raidz.  Data, parity, and spare
+space are organized in redundancy groups and distributed evenly over all of
+the devices.
+
+This feature becomes \fBactive\fR when creating a pool which uses the
+\fBdraid\fR vdev type, or when adding a new \fBdraid\fR vdev to an
+existing pool.
+.RE
+
+.sp
+.ne 2
+.na
 \fBedonr\fR
 .ad
 .RS 4n