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 

1 files changed, 20 insertions, 3 deletions

diff --git a/man/man1/ztest.1 b/man/man1/ztest.1
index 68c978ca0..3f30b3ed7 100644
--- a/man/man1/ztest.1
+++ b/man/man1/ztest.1
@@ -23,6 +23,7 @@
 .\" Copyright (c) 2009 Oracle and/or its affiliates. All rights reserved.
 .\" Copyright (c) 2009 Michael Gebetsroither <[email protected]>. All rights
 .\" reserved.
+.\" Copyright (c) 2017, Intel Corporation.
 .\"
 .TH ZTEST 1 "Aug 24, 2020" OpenZFS
 
@@ -82,13 +83,29 @@ Used alignment in test.
 .IP
 Number of mirror copies.
 .HP
-.BI "\-r" " raidz_disks" " (default: 4)"
+.BI "\-r" " raidz_disks / draid_disks" " (default: 4 / 16)"
 .IP
 Number of raidz disks.
 .HP
-.BI "\-R" " raidz_parity" " (default: 1)"
+.BI "\-R" " raid_parity" " (default: 1)"
 .IP
-Raidz parity.
+Raid parity (raidz & draid).
+.HP
+.BI "\-K" " raid_kind" " (default: 'random') raidz|draid|random"
+.IP
+The kind of RAID config to use. With 'random' the kind alternates between raidz and draid.
+.HP
+.BI "\-D" " draid_data" " (default: 4)"
+.IP
+Number of data disks in a dRAID redundancy group.
+.HP
+.BI "\-S" " draid_spares" " (default: 1)"
+.IP
+Number of dRAID distributed spare disks.
+.HP
+.BI "\-C" " vdev_class_state" " (default: random)"
+.IP
+The vdev allocation class state: special=on|off|random.
 .HP
 .BI "\-d" " datasets" " (default: 7)"
 .IP