RAID0/RAID1 step-by-step, 2.0.36 kernel, .50beta10 tools
--------------------------------------------------------
Make sure raid tools, patches, kernel
are compatible.
# rpm -qa | grep raid
raidtools-0.50beta10-2
# grep _MD /usr/src/linux/.config
CONFIG_BLK_DEV_MD=y
CONFIG_MD_LINEAR=y
CONFIG_MD_STRIPED=y
CONFIG_MD_MIRRORING=y
# CONFIG_MD_RAID5 is not set
----------------------------------------
Select similar whole disk or partition pairs
on different controllers, else poor performance.
# fdisk -l /dev/hd{e,g}
Disk /dev/hde: 255 heads, 63 sectors, 790 cylinders
Units = cylinders of 16065 * 512 bytes
Device Boot Start End Blocks Id System
/dev/hde1 1 510 4096543+ c Win95 FAT32 (LBA)
/dev/hde2 524 657 1076355 83 Linux native
/dev/hde3 511 523 104422+ 82 Linux swap
/dev/hde4 658 790 1068322+ 83 Linux native
Disk /dev/hdg: 255 heads, 63 sectors, 790 cylinders
Units = cylinders of 16065 * 512 bytes
Device Boot Start End Blocks Id System
/dev/hdg1 1 510 4096543+ c Win95 FAT32 (LBA)
/dev/hdg2 524 657 1076355 83 Linux native
/dev/hdg3 511 523 104422+ 82 Linux swap
/dev/hdg4 658 790 1068322+ 83 Linux native
----------------------------------------
Create configuration file first. 4 md devices max.
# cat /etc/raidtab
# sample raiddev configuration file
raiddev /dev/md0
raid-level 1 # pick one
#raid-level 0 #
nr-raid-disks 2
nr-spare-disks 0
chunk-size 32
device /dev/hde4
raid-disk 0
device /dev/hdg4
raid-disk 1
----------------------------------------
Raid must not be running.
# cat /proc/mdstat
Personalities : [1 linear] [2 raid0] [3 raid1]
read_ahead not set
md0 : inactive
md1 : inactive
md2 : inactive
md3 : inactive
----------------------------------------
Create raid1 structure. 'force' option is used
because partition already had a filesystem.
NOTE: no mkraid if RAID0
# mkraid -f /dev/md0
handling MD device /dev/md0
analyzing super-block
disk 0: /dev/hde4, 1068322kB, raid superblock at 1068224kB
disk 1: /dev/hdg4, 1068322kB, raid superblock at 1068224kB
initializing raid set
clearing device /dev/hde4
clearing device /dev/hdg4
(99% done; ~0:01 left 6:30 elapsed [2730.6 KB/sec])
writing raid superblock
MD ID: a92b4efc
Conforms to MD version: 0.36.4
gvalid_words: 12
Raid set ID: 4055f2b1
Creation time: Sat Jun 5 22:35:37 1999
Update time: Sat Jun 5 22:42:08 1999
State: 1 (clean)
Raid level: 1
Individual disk size: 1043MB (1068224kB)
Total number of disks: 2
Number of raid disks: 2
Number of active disks: 2
Number of working disks: 2
Number of failed disks: 0
Number of spare disks: 0
Disk 0: raid_disk 0, state: 6 (operational, active, sync)
Disk 1: raid_disk 1, state: 6 (operational, active, sync)
----------------------------------------
Now add new /dev/md0 device to kernel.
# raidadd -a
# cat /proc/mdstat
Personalities : [1 linear] [2 raid0] [3 raid1]
read_ahead not set
md0 : inactive hde4 hdg4 2136644 blocks
md1 : inactive
md2 : inactive
md3 : inactive
----------------------------------------
Now start raid. 'raid1' will be 'raid0' if RAID0.
# raidrun -a
# cat /proc/mdstat
Personalities : [1 linear] [2 raid0] [3 raid1]
read_ahead 8 sectors
md0 : active raid1 hde4 hdg4 1068224 blocks [2/2] [UU]
md1 : inactive
md2 : inactive
md3 : inactive
----------------------------------------
Don't bother with this.
# fdisk -l /dev/md0
Disk doesn't contain a valid partition table
----------------------------------------
Now make a file system. Can't do this without
valid md device and raid running.
# mke2fs -b 1024 -m 0 /dev/md0
mke2fs 1.12, 9-Jul-98 for EXT2 FS 0.5b, 95/08/09
Linux ext2 filesystem format
Filesystem label=
134144 inodes, 1068224 blocks
0 blocks (0.00%) reserved for the super user
First data block=1
Block size=1024 (log=0)
Fragment size=1024 (log=0)
131 block groups
8192 blocks per group, 8192 fragments per group
2048 inodes per group
Superblock backups stored on blocks:
8193, 16385, 24577, 32769, 40961, 49153, 57345,
...
1040385, 1048577, 1056769, 1064961
Writing inode tables: done
Writing superblocks and filesystem accounting information: done
----------------------------------------
Finally, mount filesystem as any other.
# grep raid /etc/fstab
/dev/md0 /raid ext2 defaults 1 2
# mount /raid
# df -k /raid
Filesystem 1024-blocks Used Available Capacity Mounted on
/dev/md0 1050407 13 1050394 0% /raid
----------------------------------------
General rules
1. Filesystem operations such as mount, umount, mke2fs, fsck
are valid if raid is active. % cat /proc/mdstat
To start (active): raidadd, raidrun.
2. Raid device operations such as /etc/raidtab edits,
mkraid, ckraid are valid if raid is inactive. % cat /proc/mdstat
To stop (inactive): raidstop.
4. Sources, references:
ftp://ftp.kernel.org/pub/linux/daemons/raid (use country mirror)
http://ostenfeld.dk/~jakob/Software-RAID.HOWTO/Software-RAID.HOWTO.html
/usr/doc/HOWTO/mini/Software-RAID
/usr/doc/raidtools-0.50beta10
man -k raid
ckraid (8) - checks and fixes RAID device arrays
mkraid (8) - initializes RAID device arrays
raidadd, raidrun, raidstop, (8) - command set to manage md devices.
raidtab (5) - configuration file for md (RAID) devices
[tim@asus ~]$
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