This tutorial is all about software raid-1 creation in linux.We will learn how to configure software raid-1 in linux having spare devices.In this lab we are going to use RedHat Enterprise Linux 5 to configure software raid-1 with spare device.We use spare device as a reserved disk which is used only when any of disk used in raid-1 failed.
As we know RAID-1 needs minimum of two disk and when any of disk among those two failed or crashes spare device replaces itself with that failed device or disk.
Step:1 create partitions from different disk and each partitions must have same space.
First check the number of disks available using fdisk tool.
[root@localhost ~]# fdisk -l
Disk /dev/sda: 34.3 GB, 34359738368 bytes
255 heads, 63 sectors/track, 4177 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 * 1 13 104391 83 Linux
/dev/sda2 14 4177 33447330 8e Linux LVM
Disk /dev/sdb: 2306 MB, 2306867200 bytes
255 heads, 63 sectors/track, 280 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk /dev/sdb doesn’t contain a valid partition table
Disk /dev/sdc: 2147 MB, 2147483648 bytes
255 heads, 63 sectors/track, 261 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk /dev/sdc doesn’t contain a valid partition table
Disk /dev/sdd: 2306 MB, 2306867200 bytes
255 heads, 63 sectors/track, 280 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk /dev/sdd doesn’t contain a valid partition table
Now create partitions each of 1GB from each hard disk.
From above output you can clearly have a view about the number of disks available.
/dev/sda /dev/sdb /dev/sdc and /dev/sdd it means there are 4 hard disk available now.
Now its time to create partitions from different hard disk and change the partition type to RAID-Type because we are going to use these devices to create raid device.
[root@localhost ~]# fdisk /dev/sdb Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel Building a new DOS disklabel. Changes will remain in memory only, until you decide to write them. After that, of course, the previous content won't be recoverable. Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite) Command (m for help): n Command action e extended p primary partition (1-4) p Partition number (1-4): 3 First cylinder (1-280, default 1): Using default value 1 Last cylinder or +size or +sizeM or +sizeK (1-280, default 280): +1G Command (m for help): t Selected partition 3 Hex code (type L to list codes): fd Changed system type of partition 3 to fd (Linux raid autodetect) Command (m for help): p Disk /dev/sdb: 2306 MB, 2306867200 bytes 255 heads, 63 sectors/track, 280 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/sdb3 1 123 987966 fd Linux raid autodetect Command (m for help): w The partition table has been altered! Calling ioctl() to re-read partition table. Syncing disks.
Now you must run partprobe command to save the changes in partition table as i have shown below
[root@localhost ~]# partprobe /dev/sdb
Similarly create partitions from each disks using fdisk and change there id to raid type.
root@localhost ~]# fdisk /dev/sdc
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel. Changes will remain in memory only,
until you decide to write them. After that, of course, the previous
content won’t be recoverable.
Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 3
First cylinder (1-261, default 1):
Using default value 1
Last cylinder or +size or +sizeM or +sizeK (1-261, default 261): +1G
Command (m for help): p
Disk /dev/sdc: 2147 MB, 2147483648 bytes
255 heads, 63 sectors/track, 261 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdc3 1 123 987966 83 Linux
Command (m for help): t
Selected partition 3
Hex code (type L to list codes): fd
Changed system type of partition 3 to fd (Linux raid autodetect)
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
[root@localhost ~]# partprobe /dev/sdc
[root@localhost ~]# fdisk /dev/sdd
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel. Changes will remain in memory only,
until you decide to write them. After that, of course, the previous
content won’t be recoverable.
Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-280, default 1):
Using default value 1
Last cylinder or +size or +sizeM or +sizeK (1-280, default 280): +1G
Command (m for help): t
Selected partition 1
Hex code (type L to list codes): fd
Changed system type of partition 1 to fd (Linux raid autodetect)
Command (m for help): p
Disk /dev/sdd: 2306 MB, 2306867200 bytes
255 heads, 63 sectors/track, 280 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdd1 1 123 987966 fd Linux raid autodetect
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
[root@localhost ~]# partprobe /dev/sdd
Now after you finish the partition creation you can check it whether it is properly configured or not:
[root@localhost ~]# fdisk -l
Disk /dev/sda: 34.3 GB, 34359738368 bytes
255 heads, 63 sectors/track, 4177 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 * 1 13 104391 83 Linux
/dev/sda2 14 4177 33447330 8e Linux LVM
Disk /dev/sdb: 2306 MB, 2306867200 bytes
255 heads, 63 sectors/track, 280 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdb3 1 123 987966 fd Linux raid autodetect
Disk /dev/sdc: 2147 MB, 2147483648 bytes
255 heads, 63 sectors/track, 261 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdc3 1 123 987966 fd Linux raid autodetect
Disk /dev/sdd: 2306 MB, 2306867200 bytes
255 heads, 63 sectors/track, 280 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdd1 1 123 987966 fd Linux raid autodetect
Step:2 now create raid device with spare device using mdadm command line tool.
[root@localhost ~]# mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sdb3 /dev/sdc3 --spare-devices=1 /dev/sdd1
The above code is self explanatory.
–level=1 shows it raid-1
/dev/md0 is name of raid device created
–raid-devices=2 tells two disks are used in this raid
/dev/sdb3 and /dev/sdc3 are those two disks used in raid
/dev/sdd1 is the spare device
Step3:check whether raid is properly created or not using below command.
[root@localhost ~]# mdadm –detail /dev/md0
/dev/md0:
Version : 0.90
Creation Time : Mon Dec 12 14:18:02 2016
Raid Level : raid1
Array Size : 987840 (964.85 MiB 1011.55 MB)
Used Dev Size : 987840 (964.85 MiB 1011.55 MB)
Raid Devices : 2
Total Devices : 3
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Mon Dec 12 14:18:25 2016
State : clean
Active Devices : 2
Working Devices : 3
Failed Devices : 0
Spare Devices : 1
UUID : 7547df35:f740b7f7:06234e24:013d8e13
Events : 0.2
Number Major Minor RaidDevice State
0 8 19 0 active sync /dev/sdb3
1 8 35 1 active sync /dev/sdc3
2 8 49 – spare /dev/sdd1
You can also check raid creation using below command:
[root@localhost ~]# cat /proc/mdstat Personalities : [raid1] md0 : active raid1 sdd1[2](S) sdc3[1] sdb3[0] 987840 blocks [2/2] [UU] unused devices: <none>
Step4:Now to use raid devices format it and mount it.
First create a directory where we will mount created raid-1 device.
[root@localhost ~]# mkdir /linuxtiwary
Now Format raid device using mkfs command:
[root@localhost ~]# mkfs.ext3 /dev/md0
Now mount the raid device:
[root@localhost ~]# mount /dev/md0 /linuxtiwary
Check your all mount using df command line tool:
[root@localhost ~]# df -Th Filesystem Type Size Used Avail Use% Mounted on /dev/mapper/VolGroup00-LogVol00 ext3 29G 2.0G 26G 8% / /dev/sda1 ext3 99M 12M 82M 13% /boot tmpfs tmpfs 506M 0 506M 0% /dev/shm /dev/md0 ext3 950M 18M 885M 2% /linuxtiwary
Now our raid device is ready to use.
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