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, 7 insertions, 1 deletions

diff --git a/module/zfs/metaslab.c b/module/zfs/metaslab.c
index 325f505b7..fcf1285f6 100644
--- a/module/zfs/metaslab.c
+++ b/module/zfs/metaslab.c
@@ -32,6 +32,7 @@
 #include <sys/space_map.h>
 #include <sys/metaslab_impl.h>
 #include <sys/vdev_impl.h>
+#include <sys/vdev_draid.h>
 #include <sys/zio.h>
 #include <sys/spa_impl.h>
 #include <sys/zfeature.h>
@@ -1563,6 +1564,7 @@ metaslab_block_find(zfs_btree_t *t, range_tree_t *rt, uint64_t start,
 
 #if defined(WITH_DF_BLOCK_ALLOCATOR) || \
     defined(WITH_CF_BLOCK_ALLOCATOR)
+
 /*
  * This is a helper function that can be used by the allocator to find a
  * suitable block to allocate. This will search the specified B-tree looking
@@ -1654,6 +1656,7 @@ metaslab_df_alloc(metaslab_t *msp, uint64_t size)
 		range_seg_t *rs;
 		if (zfs_btree_numnodes(&msp->ms_allocatable_by_size) == 0)
 			metaslab_size_tree_full_load(msp->ms_allocatable);
+
 		if (metaslab_df_use_largest_segment) {
 			/* use largest free segment */
 			rs = zfs_btree_last(&msp->ms_allocatable_by_size, NULL);
@@ -2616,6 +2619,10 @@ metaslab_init(metaslab_group_t *mg, uint64_t id, uint64_t object,
 	ms->ms_allocator = -1;
 	ms->ms_new = B_TRUE;
 
+	vdev_ops_t *ops = vd->vdev_ops;
+	if (ops->vdev_op_metaslab_init != NULL)
+		ops->vdev_op_metaslab_init(vd, &ms->ms_start, &ms->ms_size);
+
 	/*
 	 * We only open space map objects that already exist. All others
 	 * will be opened when we finally allocate an object for it.
@@ -5813,7 +5820,6 @@ metaslab_alloc(spa_t *spa, metaslab_class_t *mc, uint64_t psize, blkptr_t *bp,
 			metaslab_group_alloc_increment(spa,
 			    DVA_GET_VDEV(&dva[d]), zio, flags, allocator);
 		}
-
 	}
 	ASSERT(error == 0);
 	ASSERT(BP_GET_NDVAS(bp) == ndvas);