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, 8 insertions, 2 deletions

diff --git a/module/zcommon/zfeature_common.c b/module/zcommon/zfeature_common.c
index 97ddacbab..599791d49 100644
--- a/module/zcommon/zfeature_common.c
+++ b/module/zcommon/zfeature_common.c
@@ -576,7 +576,7 @@ zpool_feature_init(void)
 
 	zfeature_register(SPA_FEATURE_DEVICE_REBUILD,
 	    "org.openzfs:device_rebuild", "device_rebuild",
-	    "Support for sequential device rebuilds",
+	    "Support for sequential mirror/dRAID device rebuilds",
 	    ZFEATURE_FLAG_READONLY_COMPAT, ZFEATURE_TYPE_BOOLEAN, NULL);
 
 	{
@@ -589,6 +589,10 @@ zpool_feature_init(void)
 	    "zstd compression algorithm support.",
 	    ZFEATURE_FLAG_PER_DATASET, ZFEATURE_TYPE_BOOLEAN, zstd_deps);
 	}
+
+	zfeature_register(SPA_FEATURE_DRAID,
+	    "org.openzfs:draid", "draid", "Support for distributed parity RAID",
+	    ZFEATURE_FLAG_MOS, ZFEATURE_TYPE_BOOLEAN, NULL);
 }
 
 #if defined(_KERNEL)
diff --git a/module/zcommon/zfs_namecheck.c b/module/zcommon/zfs_namecheck.c
index f8625042a..0011a971c 100644
--- a/module/zcommon/zfs_namecheck.c
+++ b/module/zcommon/zfs_namecheck.c
@@ -442,7 +442,9 @@ pool_namecheck(const char *pool, namecheck_err_t *why, char *what)
 		return (-1);
 	}
 
-	if (strcmp(pool, "mirror") == 0 || strcmp(pool, "raidz") == 0) {
+	if (strcmp(pool, "mirror") == 0 ||
+	    strcmp(pool, "raidz") == 0 ||
+	    strcmp(pool, "draid") == 0) {
 		if (why)
 			*why = NAME_ERR_RESERVED;
 		return (-1);