21.14.3. Updating the Size of Your Multipath Device
If multipathing is enabled on your system, you will also need to reflect the change in logical unit size to the logical unit's corresponding multipath device (after resizing the logical unit). For Red Hat Enterprise Linux 5.3 (or later), you can do this through
multipathd. To do so, first ensure that
multipathd is running using
service multipathd status. Once you've verified that
multipathd is operational, run the following command:
multipathd -k"resize map
variable is the corresponding multipath entry of your device in
/dev/mapper. Depending on how multipathing is set up on your system,
can be either of two formats:
is the corresponding entry of your device (for example,
a WWID; for example,
To determine which multipath entry corresponds to your resized logical unit, run
multipath -ll. This displays a list of all existing multipath entries in the system, along with the major and minor numbers of their corresponding devices.
Do not use
multipathd -k"resize map if there are any commands queued to
. That is, do not use this command when the
no_path_retry parameter (in
/etc/multipath.conf) is set to
"queue", and there are no active paths to the device.
If your system is using Red Hat Enterprise Linux 5.0-5.2, you will need to perform the following procedure to instruct the
multipathd daemon to recognize (and adjust to) the changes you made to the resized logical unit:
Procedure 21.4. Resizing the Corresponding Multipath Device (Required for Red Hat Enterprise Linux 5.0 - 5.2)
Dump the device mapper table for the multipathed device using:
Save the dumped device mapper table as
. This table will be re-loaded and edited later.
Examine the device mapper table. Note that the first two numbers in each line correspond to the start and end sectors of the disk, respectively.
Suspend the device mapper target:
Open the device mapper table you saved earlier (i.e.
). Change the second number (i.e. the disk end sector) to reflect the new number of 512 byte sectors in the disk. For example, if the new disk size is 2GB, change the second number to 4194304.
Reload the modified device mapper table:
Resume the device mapper target: