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[PATCH] md: support stripe/offset mode in raid10

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The "industry standard" DDF format allows for a stripe/offset layout where
data is duplicated on different stripes.  e.g.

  A  B  C  D
  D  A  B  C
  E  F  G  H
  H  E  F  G

(columns are drives, rows are stripes, LETTERS are chunks of data).

This is similar to raid10's 'far' mode, but not quite the same.  So enhance
'far' mode with a 'far/offset' option which follows the layout of DDFs
stripe/offset.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
NeilBrown
2006-06-26 00:27:41 -07:00
committed by Linus Torvalds
parent 7c7546ccf6
commit c93983bf51
2 changed files with 49 additions and 22 deletions
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7
include/linux/raid/raid10.h
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@ -24,11 +24,16 @@ struct r10_private_data_s {
int far_copies; /* number of copies layed out
* at large strides across drives
*/
int far_offset; /* far_copies are offset by 1 stripe
* instead of many
*/
int copies; /* near_copies * far_copies.
* must be <= raid_disks
*/
sector_t stride; /* distance between far copies.
* This is size / far_copies
* This is size / far_copies unless
* far_offset, in which case it is
* 1 stripe.
*/
int chunk_shift; /* shift from chunks to sectors */