HP Serviceguard Extended Distance Cluster for Linux A.12.00.00 Deployment Guide, March 2014

hpdev/mylink-sdc \

disk/by-id/scsi-3600805f3000b9510a6d7f8a6cdb70054-part1 \ disk/by

-path/pci-0000:06:01.0-scsi-0:0:1:30-part1

Run the following command to remove a failed component device from the MD array:

# mdadm - -remove <md device name> <md_mirror_component_persistent_name>

In this example:

# mdadm --remove /dev/md0 /dev/hpdev/mylink-sdc1

This command removes the failed mirrored disk from the array.

Example 3 Removing a failed MD component disk from /dev/md0 array

To remove a failed MD component disk from /dev/md0, run the following command:

# mdadm –-remove /dev/md0 /dev/hpdev/sde

Following is an example of the status message that is displayed when a failed component is

removed from the MD array:

[root@dlhct1 dev]# cat /proc/mdstat

Personalities : [raid1]

md0 : active raid1 sdf[0]

9766784 blocks [2/1] [U_]

unused devices: <none>

A.4.1 Adding a Mirror Component Device

As mentioned earlier, in certain failure scenarios, you need to remove a failed mirror disk

component, repair it and then add it back into an MD array. Run the following command to add

a mirror component back into the MD array:

# mdadm - -add <md device name> <md_mirror_component_persistent_name>

Example 4 Adding a new disk as an MD component to /dev/md0 array

To add a new disk to the/dev/md0 array, run the following command:

# mdadm - -add /dev/md0 /dev/hpdev/sde

Following is an example of the status message displayed in the /proc/mdstat file once the disk

is added:

Personalities : [raid1]

md0 : active raid1 sde[2] sdf[0]

9766784 blocks [2/1] [U_]

[=>...................] recovery = 8.9% (871232/9766784) finish=2.7min

speed=54452K/sec

unused devices: <none>

A.5 Speeding up MD Device Builds and Re-syncing

The /proc/sys/dev/raid/speed_limit_min configuration file shows the current "goal"

rebuild speed when non-rebuild activity is available on an array.

To view the current speed limit:

# sysctl dev.raid.speed_limit_min

# sysctl dev.raid.speed_limit_max

To increase the speed limit:

# echo value > /proc/sys/dev/raid/speed_limit_min

# sysctl -w dev.raid.speed_limit_min=value

For example, to set the value to 50000 Kb/s:

A.5 Speeding up MD Device Builds and Re-syncing 51