vserver 1.9.5.x5

[linux-2.6.git] / Documentation / md.txt

diff --git a/Documentation/md.txt b/Documentation/md.txt
index 2032313..e2b5369 100644 (file)
--- a/Documentation/md.txt
+++ b/Documentation/md.txt
@@ -2,6 +2,8 @@ Tools that manage md devices can be found at
    http://www.<country>.kernel.org/pub/linux/utils/raid/....
 
 
+Boot time assembly of RAID arrays
+---------------------------------
 
 You can boot with your md device with the following kernel command
 lines:
@@ -11,6 +13,8 @@ for old raid arrays without persistent superblocks:
 
 for raid arrays with persistent superblocks
   md=<md device no.>,dev0,dev1,...,devn
+or, to assemble a partitionable array:
+  md=d<md device no.>,dev0,dev1,...,devn
   
 md device no. = the number of the md device ... 
               0 means md0, 
@@ -34,15 +38,31 @@ A possible loadlin line (Harald Hoyer <HarryH@Royal.Net>)  looks like this:
 
 e:\loadlin\loadlin e:\zimage root=/dev/md0 md=0,0,4,0,/dev/hdb2,/dev/hdc3 ro
 
--------------------------------
+
+Boot time autodetection of RAID arrays
+--------------------------------------
+
+When md is compiled into the kernel (not as module), partitions of
+type 0xfd are scanned and automatically assembled into RAID arrays.
+This autodetection may be suppressed with the kernel parameter
+"raid=noautodetect".  As of kernel 2.6.9, only drives with a type 0
+superblock can be autodetected and run at boot time.
+
+The kernel parameter "raid=partitionable" (or "raid=part") means
+that all auto-detected arrays are assembled as partitionable.
+
+
+Superblock formats
+------------------
+
 The md driver can support a variety of different superblock formats.
-(It doesn't yet, but it can)
+Currently, it supports superblock formats "0.90.0" and the "md-1" format
+introduced in the 2.5 development series.
 
-The kernel does *NOT* autodetect which format superblock is being
-used. It must be told.
+The kernel will autodetect which format superblock is being used.
 
 Superblock format '0' is treated differently to others for legacy
-reasons.
+reasons - it is the original superblock format.
 
 
 General Rules - apply for all superblock formats
@@ -50,6 +70,7 @@ General Rules - apply for all superblock formats
 
 An array is 'created' by writing appropriate superblocks to all
 devices.
+
 It is 'assembled' by associating each of these devices with an
 particular md virtual device.  Once it is completely assembled, it can
 be accessed.
@@ -57,10 +78,10 @@ be accessed.
 An array should be created by a user-space tool.  This will write
 superblocks to all devices.  It will usually mark the array as
 'unclean', or with some devices missing so that the kernel md driver
-can create approrpriate redundancy (copying in raid1, parity
+can create appropriate redundancy (copying in raid1, parity
 calculation in raid4/5).
 
-When an array is assembled, it is first initialised with the
+When an array is assembled, it is first initialized with the
 SET_ARRAY_INFO ioctl.  This contains, in particular, a major and minor
 version number.  The major version number selects which superblock
 format is to be used.  The minor number might be used to tune handling
@@ -82,15 +103,16 @@ array using HOT_REMOVE_DISK.
 
 
 Specific Rules that apply to format-0 super block arrays, and
-       arrays with no superblock (non-presistant).
+       arrays with no superblock (non-persistent).
 -------------------------------------------------------------
 
 An array can be 'created' by describing the array (level, chunksize
 etc) in a SET_ARRAY_INFO ioctl.  This must has major_version==0 and
 raid_disks != 0.
-Then uninitialised devices can be added with ADD_NEW_DISK.  The
+
+Then uninitialized devices can be added with ADD_NEW_DISK.  The
 structure passed to ADD_NEW_DISK must specify the state of the device
 and it's role in the array.
 
-One started with RUN_ARRAY, uninitialised spares can be added with
+Once started with RUN_ARRAY, uninitialized spares can be added with
 HOT_ADD_DISK.