diff options
Diffstat (limited to 'Documentation/md.txt')
| -rw-r--r-- | Documentation/md.txt | 42 |
1 files changed, 22 insertions, 20 deletions
diff --git a/Documentation/md.txt b/Documentation/md.txt index 0668f9dc9d29..2202f5dc8ac2 100644 --- a/Documentation/md.txt +++ b/Documentation/md.txt @@ -62,7 +62,7 @@ be reconstructed (due to no parity). For this reason, md will normally refuse to start such an array. This requires the sysadmin to take action to explicitly start the array -desipite possible corruption. This is normally done with +despite possible corruption. This is normally done with mdadm --assemble --force .... This option is not really available if the array has the root @@ -154,11 +154,12 @@ contains further md-specific information about the device. All md devices contain: level - a text file indicating the 'raid level'. This may be a standard - numerical level prefixed by "RAID-" - e.g. "RAID-5", or some - other name such as "linear" or "multipath". + a text file indicating the 'raid level'. e.g. raid0, raid1, + raid5, linear, multipath, faulty. If no raid level has been set yet (array is still being - assembled), this file will be empty. + assembled), the value will reflect whatever has been written + to it, which may be a name like the above, or may be a number + such as '0', '5', etc. raid_disks a text file with a simple number indicating the number of devices @@ -174,7 +175,7 @@ All md devices contain: raid levels that involve striping (1,4,5,6,10). The address space of the array is conceptually divided into chunks and consecutive chunks are striped onto neighbouring devices. - The size should be atleast PAGE_SIZE (4k) and should be a power + The size should be at least PAGE_SIZE (4k) and should be a power of 2. This can only be set while assembling an array component_size @@ -192,14 +193,6 @@ All md devices contain: 1.2 (newer format in varying locations) or "none" indicating that the kernel isn't managing metadata at all. - level - The raid 'level' for this array. The name will often (but not - always) be the same as the name of the module that implements the - level. To be auto-loaded the module must have an alias - md-$LEVEL e.g. md-raid5 - This can be written only while the array is being assembled, not - after it is started. - layout The "layout" for the array for the particular level. This is simply a number that is interpretted differently by different @@ -221,8 +214,8 @@ All md devices contain: safe_mode_delay When an md array has seen no write requests for a certain period of time, it will be marked as 'clean'. When another write - request arrive, the array is marked as 'dirty' before the write - commenses. This is known as 'safe_mode'. + request arrives, the array is marked as 'dirty' before the write + commences. This is known as 'safe_mode'. The 'certain period' is controlled by this file which stores the period as a number of seconds. The default is 200msec (0.200). Writing a value of 0 disables safemode. @@ -314,8 +307,8 @@ Each directory contains: This applies only to raid1 arrays. spare - device is working, but not a full member. This includes spares that are in the process - of being recoverred to - This list make grow in future. + of being recovered to + This list may grow in future. This can be written to. Writing "faulty" simulates a failure on the device. Writing "remove" removes the device from the array. @@ -337,7 +330,7 @@ Each directory contains: This gives the role that the device has in the array. It will either be 'none' if the device is not active in the array (i.e. is a spare or has failed) or an integer less than the - 'raid_disks' number for the array indicating which possition + 'raid_disks' number for the array indicating which position it currently fills. This can only be set while assembling an array. A device for which this is set is assumed to be working. @@ -360,7 +353,7 @@ in the array. These are named rdNN -where 'NN' is the possition in the array, starting from 0. +where 'NN' is the position in the array, starting from 0. So for a 3 drive array there will be rd0, rd1, rd2. These are symbolic links to the appropriate 'dev-XXX' entry. Thus, for example, @@ -410,6 +403,15 @@ also have than sectors, this my be larger than the number of actual errors by a factor of the number of sectors in a page. + bitmap_set_bits + If the array has a write-intent bitmap, then writing to this + attribute can set bits in the bitmap, indicating that a resync + would need to check the corresponding blocks. Either individual + numbers or start-end pairs can be written. Multiple numbers + can be separated by a space. + Note that the numbers are 'bit' numbers, not 'block' numbers. + They should be scaled by the bitmap_chunksize. + Each active md device may also have attributes specific to the personality module that manages it. These are specific to the implementation of the module and could |