diff options
author | Neil Brown <neilb@suse.de> | 2006-05-15 02:46:54 +0000 |
---|---|---|
committer | Neil Brown <neilb@suse.de> | 2006-05-15 02:46:54 +0000 |
commit | b578481ca382959da894ebdd91c5e5f45d50374d (patch) | |
tree | 957c835dfdf7632dc05ea91ba8ba82137fd4ceed /md.4 | |
parent | a99d6b669c4dbe7f9609c720c9f114e278b4388b (diff) |
Support new offset layout for raid10
Requires 2.6.18.
Signed-off-by: Neil Brown <neilb@suse.de>
Diffstat (limited to 'md.4')
-rw-r--r-- | md.4 | 10 |
1 files changed, 9 insertions, 1 deletions
@@ -203,7 +203,8 @@ drives. When configuring a RAID10 array it is necessary to specify the number of replicas of each data block that are required (this will normally -be 2) and whether the replicas should be 'near' or 'far'. +be 2) and whether the replicas should be 'near', 'offset' or 'far'. +(Note that the 'offset' layout is only available from 2.6.18). When 'near' replicas are chosen, the multiple copies of a given chunk are laid out consecutively across the stripes of the array, so the two @@ -220,6 +221,13 @@ of any given block are on different drives. The 'far' arrangement can give sequential read performance equal to that of a RAID0 array, but at the cost of degraded write performance. +When 'offset' replicas are chosen, the multiple copies of a given +chunk are laid out on consecutive drives and at consecutive offsets. +Effectively each stripe is duplicated and the copies are offset by one +device. This should give similar read characteristics to 'far' if a +suitably large chunk size is used, but without as much seeking for +writes. + It should be noted that the number of devices in a RAID10 array need not be a multiple of the number of replica of each data block, those there must be at least as many devices as replicas. |