User:Svamberg/Software RAID

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You might want to read Setup_harddisks_2 for an update on the status of a fai integrated solution.

Contents

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Prerequisite

  • mdadm package in NFSROOT
  • your install and running kernel must supported software raid
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Install

You need two hooks if you want to support software raids based on mdadm. Your kernels need to support software raid.

  • get the main hook mountdisks.SW_RAID and store it in the $FAI/hooks/ directory
  • save the following lines as mountdisks.SW_RAID.source in the $FAI/hooks directory 
#!/bin/sh
. $LOGDIR/disk_var.sh
  • add class SW_RAID to your $FAI/class/ configuration
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Configure

Configuration is stored as the $SW_RAID_CONFIG variable, a syntax of which is 

md_raid_device[raid_options]=devices:mountpoint:filesystem[,mkfs_options]:mount_options:boot

  raid_options - raid_level[,mdadm_option[,next_mdadm_option[,...]]]
  devices - first_device,[next_device,[,...]]][;first_spare_device[,next_spare_device[,...]]]

For example: 

SW_RAID_CONFIG="
md0[mirror]=/dev/sda1,/dev/sdb1:/boot:ext3::
md1[mirror]=/dev/sda2,/dev/sdb2:/:ext3:rw,errors=remount-ro:boot
md2[mirror]=/dev/sda5,/dev/sdb5:none:swap::
md3[linear]=/dev/sda7,/dev/sdb7:/mnt/data:ext3,-T news::
"
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Example

As an example, let's assume we have two identical disks. We need all raids in mirror.

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Partitioning

Before using raid you need to partition the disks by editing the $FAI/disk_config file. 

# <type> <mountpoint> <size in mb> [mount options]     [;extra options]

disk_config sda
primary  /boot        100        rw                     ; boot -j ext3
primary  /            10000      rw,errors=remount-ro ; -j ext3
logical  -            2000                               
logical  -            2000                        
logical  -            1024-      
logical  -            1000

disk_config sdb
primary  -            100        
primary  -            10000      
logical  -            2000                         
logical  -            2000                         
logical  -            1024-     
logical  -            1000
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Configure raids

Add the raid configuration into the .var file (in $FAI/class directory): 

SW_RAID_CONFIG="
md0[mirror]=/dev/sda1,/dev/sdb1:/boot:ext3::
md1[mirror]=/dev/sda2,/dev/sdb2:/:ext3:rw,errors=remount-ro:boot
md3[mirror]=/dev/sda5,/dev/sdb5:none:swap::
md4[mirror]=/dev/sda6,/dev/sdb6:none:swap::
md5[mirror]=/dev/sda7,/dev/sdb7:/var:ext3::
md6[mirror]=/dev/sda8,/dev/sdb8:/var/cache/openafs:ext3::
"
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Result

After installation /proc/mdstat says: 

Personalities : [linear] [raid0] [raid1] [raid5] 
md1 : active raid1 sde2[1] sdd2[0]
      10241344 blocks [2/2] [UU]
      
md3 : active raid1 sde5[1] sdd5[0]
      2048192 blocks [2/2] [UU]
      
md4 : active raid1 sde6[1] sdd6[0]
      2048192 blocks [2/2] [UU]
      
md5 : active raid1 sde7[1] sdd7[0]
      56211328 blocks [2/2] [UU]
      
md6 : active raid1 sde8[1] sdd8[0]
      1028032 blocks [2/2] [UU]
      
md0 : active raid1 sde1[1] sdd1[0]
      104320 blocks [2/2] [UU]
      
unused devices: <none>
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