Illumos #1051: zfs should handle imbalanced luns

Today zfs tries to allocate blocks evenly across all devices.
This means when devices are imbalanced zfs will use lots of
CPU searching for space on devices which tend to be pretty
full.  It should instead fail quickly on the full LUNs and
move onto devices which have more availability.

Reviewed by: Eric Schrock <[email protected]>
Reviewed by: Matt Ahrens <[email protected]>
Reviewed by: Adam Leventhal <[email protected]>
Reviewed by: Albert Lee <[email protected]>
Reviewed by: Gordon Ross <[email protected]>
Approved by: Garrett D'Amore <[email protected]>

References to Illumos issue and patch:
- https://www.illumos.org/issues/510
- https://github.com/illumos/illumos-gate/commit/5ead3ed965

Signed-off-by: Brian Behlendorf <[email protected]>
Issue #340

1 files changed, 3 insertions, 0 deletions

diff --git a/include/sys/metaslab.h b/include/sys/metaslab.h
index 583d6303b..2cf4d2b48 100644
--- a/include/sys/metaslab.h
+++ b/include/sys/metaslab.h
@@ -20,6 +20,7 @@
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2011 by Delphix. All rights reserved.
  */
 
 #ifndef _SYS_METASLAB_H
@@ -47,6 +48,8 @@ extern void metaslab_sync_reassess(metaslab_group_t *mg);
 #define	METASLAB_HINTBP_FAVOR	0x0
 #define	METASLAB_HINTBP_AVOID	0x1
 #define	METASLAB_GANG_HEADER	0x2
+#define	METASLAB_GANG_CHILD	0x4
+#define	METASLAB_GANG_AVOID	0x8
 
 extern int metaslab_alloc(spa_t *spa, metaslab_class_t *mc, uint64_t psize,
     blkptr_t *bp, int ncopies, uint64_t txg, blkptr_t *hintbp, int flags);