mdadm使用详解及RAID 5简单分析

This usage will initialise a new md array, associate some
devices with it, and activate the array.   In order to create an
array with some devices missing, use the special word ‘missing’ in
place of the relevant device name.

Before devices are added, they are checked to see if they already contain
raid superblocks or filesystems.  They are also checked to see if
the variance in device size exceeds 1%.
If any discrepancy is found, the user will be prompted for confirmation
before the array is created.  The presence of a ‘–run’ can override this
caution.

If the –size option is given then only that many kilobytes of each
device is used, no matter how big each device is.
If no –size is given, the apparent size of the smallest drive given
is used for raid level 1 and greater, and the full device is used for
other levels.

Options that are valid with –create (-C) are:
–bitmap=          : Create a bitmap for the array with the given filename
–chunk=      -c   : chunk size of kibibytes
–rounding=        : rounding factor for linear array (==chunk size)
–level=      -l   : raid level: 0,1,4,5,6,linear,multipath and synonyms
–parity=     -p   : raid5/6 parity algorithm: {left,right}-{,a}symmetric
–layout=          : same as –parity
–raid-devices= -n : number of active devices in array
–spare-devices= -x: number of spares (eXtras) devices in initial array
–size=       -z   : Size (in K) of each drive in RAID1/4/5/6/10 – optional
–force       -f   : Honour devices as listed on command line.  Don’t
: insert a missing drive for RAID5.
–run         -R   : insist of running the array even if not all
: devices are present or some look odd.
–readonly    -o   : start the array readonly – not supported yet.
–name=       -N   : Textual name for array – max 32 characters
–bitmap-chunk=    : bitmap chunksize in Kilobytes.
–delay=      -d   : bitmap update delay in seconds.

Personalities : [raid5]
read_ahead 1024 sectors
md0 : active raid5 sdd[4] sde[3] sdc[1] sdb[0]
16777088 blocks level 5, 64k chunk, algorithm 2 [3/2] [UU_]
[====>…………….]  recovery = 24.0% (2016364/8388544) finish=10.2min
speed=10324K/sec
unused devices: <none>
[root@localhost mdadm-2.6.2]#

Writing inode tables: done
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 34 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.
You have new mail in /var/spool/mail/root

Update Time : Thu May 24 13:45:36 2007
State : active, degraded, recovering
Active Devices : 2
Working Devices : 4
Failed Devices : 1
Spare Devices : 2

Layout : left-symmetric
Chunk Size : 64K

Rebuild Status : 16% complete

UUID : 4b15050e:7d0c477d:98ed7d00:0f3c29e4
Events : 0.2

Number   Major   Minor   RaidDevice State
0       8       16        0      active sync   /dev/sdb
1       8       32        1      active sync   /dev/sdc
2       0        0        2      removed

3       8       64        3      spare   /dev/sde
4       8       48        4      spare   /dev/sdd

Personalities : [raid5]
read_ahead 1024 sectors
md0 : active raid5 sdd[4] sde[3] sdc[1] sdb[0]
16777088 blocks level 5, 64k chunk, algorithm 2 [3/2] [UU_]
[==============>……]  recovery = 72.3% (6067444/8388544) finish=3.7min
speed=10324K/sec
unused devices: <none>

Personalities : [raid5]
read_ahead 1024 sectors
md0 : active raid5 sdd[2] sde[3] sdc[1] sdb[0]
16777088 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU]

unused devices: <none>

Update Time : Thu May 24 13:59:48 2007
State : active
Active Devices : 3
Working Devices : 4
Failed Devices : 1
Spare Devices : 1

Layout : left-symmetric
Chunk Size : 64K

UUID : 4b15050e:7d0c477d:98ed7d00:0f3c29e4
Events : 0.3

Number   Major   Minor   RaidDevice State
0       8       16        0      active sync   /dev/sdb
1       8       32        1      active sync   /dev/sdc
2       8       48        2      active sync   /dev/sdd

3       8       64        3      spare   /dev/sde

This usage is for managing the component devices within an array.
The –manage option is not needed and is assumed if the first argument
is a device name or a management option.
The first device listed will be taken to be an md array device, and
subsequent devices are (potential) components of that array.

Options that are valid with management mode are:
–add         -a   : hotadd subsequent devices to the array
–remove      -r   : remove subsequent devices, which must not be active
–fail        -f   : mark subsequent devices a faulty
–set-faulty       : same as –fail
–run         -R   : start a partially built array
–stop        -S   : deactivate array, releasing all resources
–readonly    -o   : mark array as readonly
–readwrite   -w   : mark array as readwrite
[root@localhost eric4ever]# mdadm –fail –help
Usage: mdadm arraydevice options component devices…

This usage is for managing the component devices within an array.
The –manage option is not needed and is assumed if the first argument
is a device name or a management option.
The first device listed will be taken to be an md array device, and
subsequent devices are (potential) components of that array.

Options that are valid with management mode are:
–add         -a   : hotadd subsequent devices to the array
–remove      -r   : remove subsequent devices, which must not be active
–fail        -f   : mark subsequent devices a faulty
–set-faulty       : same as –fail
–run         -R   : start a partially built array
–stop        -S   : deactivate array, releasing all resources
–readonly    -o   : mark array as readonly
–readwrite   -w   : mark array as readwrite

Update Time : Thu May 24 14:07:55 2007
State : active, degraded, recovering
Active Devices : 2
Working Devices : 3
Failed Devices : 2
Spare Devices : 1

Layout : left-symmetric
Chunk Size : 64K

Rebuild Status : 3% complete

UUID : 4b15050e:7d0c477d:98ed7d00:0f3c29e4
Events : 0.6

Number   Major   Minor   RaidDevice State
0       8       16        0      faulty spare   /dev/sdb
1       8       32        1      active sync   /dev/sdc
2       8       48        2      active sync   /dev/sdd

3       8       64        3      spare rebuilding   /dev/sde

Update Time : Thu May 24 14:08:27 2007
State : active, degraded, recovering
Active Devices : 2
Working Devices : 4
Failed Devices : 1
Spare Devices : 2

Layout : left-symmetric
Chunk Size : 64K

Rebuild Status : 11% complete

UUID : 4b15050e:7d0c477d:98ed7d00:0f3c29e4
Events : 0.8

Number   Major   Minor   RaidDevice State
0       0        0        0      removed
1       8       32        1      active sync   /dev/sdc
2       8       48        2      active sync   /dev/sdd

3       8       64        3      spare   /dev/sde
4       8       16        4      spare   /dev/sdb

Update Time : Thu May 24 14:08:27 2007
State : active
Active Devices : 2
Working Devices : 4
Failed Devices : 1
Spare Devices : 2
Checksum : a6a19662 – correct
Events : 0.8

Layout : left-symmetric
Chunk Size : 64K

Number   Major   Minor   RaidDevice State
this     4       8       16        4      spare   /dev/sdb

0     0       0        0        0      faulty removed
1     1       8       32        1      active sync   /dev/sdc
2     2       8       48        2      active sync   /dev/sdd
3     3       8       64        3      spare   /dev/sde
4     4       8       16        4      spare   /dev/sdb

Update Time : Thu May 24 14:21:54 2007
State : active
Active Devices : 3
Working Devices : 4
Failed Devices : 1
Spare Devices : 1

Layout : left-symmetric
Chunk Size : 64K

UUID : 4b15050e:7d0c477d:98ed7d00:0f3c29e4
Events : 0.9

Number   Major   Minor   RaidDevice State
0       8       64        0      active sync   /dev/sde
1       8       32        1      active sync   /dev/sdc
2       8       48        2      active sync   /dev/sdd

4       8       16        4      spare   /dev/sdb
[root@localhost eric4ever]# cat /proc/mdstat
Personalities : [raid5]
read_ahead 1024 sectors
md0 : active raid5 sdb[4] sde[0] sdd[2] sdc[1]
16777088 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU]

unused devices: <none>