linux software raid 5 quick guide

Here will create a raid 5 setup with three drives for redundant storage using mdadm (not raidtools). This example does not include putting your O.S. root partion on the raid device. It is only for a volume to be mounted by Linux which boots off of another device.

Number of drives: 3 Number of spare drives: 0 All drives same size All space used on all drives devices to be used in this example: sdb sdc sdd

kernel config

Check for support If your system has RAID support, you should have a file called /proc/mdstat. If you do not have that file, maybe your kernel does not have RAID support. For more info on configuring your linux kernel for software raid, go here

prepare disks

check existing partition tables

this command will dump the partitions for all three drives

# fdisk -l /dev/sd[bcd]

create three raid partions

assuming they don't already exist...

linux # fdisk /dev/sdb

The device presents a logical sector size that is smaller than
the physical sector size. Aligning to a physical sector (or optimal
I/O) size boundary is recommended, or performance may be impacted.
Welcome to fdisk (util-linux 2.22.2).

Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): n
Partition type:
  p   primary (0 primary, 0 extended, 4 free)
  e   extended
Select (default p): 
Using default response p
Partition number (1-4, default 1): 
Using default value 1
First sector (2048-1953525167, default 2048): 
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-1953525167, default 1953525167): 
Using default value 1953525167
Partition 1 of type Linux and of size 931.5 GiB is set

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): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.

Links

this guide is recommended by the linux kernel help... [Software RAID HOWTO]