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authorJonathan Brassow <jbrassow@redhat.com>2013-02-21 13:28:10 +1100
committerNeilBrown <neilb@suse.de>2013-02-26 11:55:33 +1100
commit9a3152ab024867100f2f50d124b998d05fb1c3f6 (patch)
tree15b97c56d117340fa5db609ced6e0d51a91f2f37 /Documentation/device-mapper
parent475901aff15841fb0a81e7546517407779a9b061 (diff)
MD RAID10: Improve redundancy for 'far' and 'offset' algorithms (part 2)
MD RAID10: Improve redundancy for 'far' and 'offset' algorithms (part 2) This patch addresses raid arrays that have a number of devices that cannot be evenly divided by 'far_copies'. (E.g. 5 devices, far_copies = 2) This case must be handled differently because it causes that last set to be of a different size than the rest of the sets. We must compute a new modulo for this last set so that copied chunks are properly wrapped around. Example use_far_sets=1, far_copies=2, near_copies=1, devices=5: "far" algorithm dev1 dev2 dev3 dev4 dev5 ==== ==== ==== ==== ==== [ A B ] [ C D E ] [ G H ] [ I J K ] ... [ B A ] [ E C D ] --> nominal set of 2 and last set of 3 [ H G ] [ K I J ] []'s show far/offset sets Signed-off-by: Jonathan Brassow <jbrassow@redhat.com> Signed-off-by: NeilBrown <neilb@suse.de>
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