diff options
Diffstat (limited to 'md.4')
| -rw-r--r-- | md.4 | 14 |
1 files changed, 10 insertions, 4 deletions
@@ -584,8 +584,12 @@ array (so the stripes are wider), changing the chunk size (so stripes are deeper or shallower), or changing the arrangement of data and parity (possibly changing the raid level, e.g. 1 to 5 or 5 to 6). -As of Linux 2.6.17, md can reshape a raid5 array to have more -devices. Other possibilities may follow in future kernels. +As of Linux 2.6.35, md can reshape a RAID4, RAID5, or RAID6 array to +have a different number of devices (more or fewer) and to have a +different layout or chunk size. It can also convert between these +different RAID levels. It can also convert between RAID0 and RAID10, +and between RAID0 and RAID4 or RAID5. +Other possibilities may follow in future kernels. During any stripe process there is a 'critical section' during which live data is being overwritten on disk. For the operation of @@ -595,6 +599,9 @@ and new number of devices). After this critical section is passed, data is only written to areas of the array which no longer hold live data \(em the live data has already been located away. +For a reshape which reduces the number of devices, the 'critical +section' is at the end of the reshape process. + md is not able to ensure data preservation if there is a crash (e.g. power failure) during the critical section. If md is asked to start an array which failed during a critical section of restriping, @@ -622,8 +629,7 @@ For operations that do not change the size of the array, like simply increasing chunk size, or converting RAID5 to RAID6 with one extra device, the entire process is the critical section. In this case, the restripe will need to progress in stages, as a section is suspended, -backed up, -restriped, and released; this is not yet implemented. +backed up, restriped, and released. .SS SYSFS INTERFACE Each block device appears as a directory in |