More ashift improvements

This commit allow higher ashift values (up to 16) in 'zpool create'

The ashift value was previously limited to 13 (8K block) in b41c990
because the limited number of uberblocks we could fit in the
statically sized (128K) vdev label ring buffer could prevent the
ability the safely roll back a pool to recover it.

Since b02fe35 the largest uberblock size we support is 8K: this
allow us to store a minimum number of 16 uberblocks in the vdev
label, even with higher ashift values.

Additionally change 'ashift' pool property behaviour: if set it will
be used as the default hint value in subsequent vdev operations
('zpool add', 'attach' and 'replace'). A custom ashift value can still
be specified from the command line, if desired.

Finally, fix a bug in add-o_ashift.ksh caused by a missing variable.

Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: loli10K <[email protected]>
Closes #2024 
Closes #4205 
Closes #4740 
Closes #5763 

1 files changed, 3 insertions, 3 deletions

diff --git a/include/sys/spa.h b/include/sys/spa.h
index e2f27ed60..22a396689 100644
--- a/include/sys/spa.h
+++ b/include/sys/spa.h
@@ -126,11 +126,11 @@ _NOTE(CONSTCOND) } while (0)
  * which can only be set at vdev creation time. Physical writes are always done
  * according to it, which makes 2^ashift the smallest possible IO on a vdev.
  *
- * We currently allow values ranging from 512 bytes (2^9 = 512) to 8 KiB
- * (2^13 = 8,192).
+ * We currently allow values ranging from 512 bytes (2^9 = 512) to 64 KiB
+ * (2^16 = 65,536).
  */
 #define	ASHIFT_MIN		9
-#define	ASHIFT_MAX		13
+#define	ASHIFT_MAX		16
 
 /*
  * Size of block to hold the configuration data (a packed nvlist)