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Red Hat Enterprise Linux 9 Essentials Book now available.

Purchase a copy of Red Hat Enterprise Linux 9 (RHEL 9) Essentials

Red Hat Enterprise Linux 9 Essentials Print and eBook (PDF) editions contain 34 chapters and 298 pages

Preview Book

Chapter 5. DM-Multipath Administration and Troubleshooting

This chapter will provide information on administering DM-Multipath on a running system. It includes sections on the following topics:
  • Resizing an Online Multipath Device
  • The Multipath Daemon
  • Issues with Large Number of LUNs
  • Issues with queue_if_no_path feature
  • Multipath Command Output
  • Multipath Queries with multipath Command
  • Multipath Command Options
  • Multipath Queries with dmsetup Command
  • Troubleshooting with the multipathd Interactive Console

5.1. Resizing an Online Multipath Device

If you need to resize an online multipath device, use the following procedure.
  1. Resize your physical device.
  2. Use the following command to find the paths to the LUN:
    # multipath -l
  3. Resize your paths. For SCSI devices, writing a 1 to the rescan file for the device causes the SCSI driver to rescan, as in the following command:
    # echo 1 > /sys/block/device_name/device/rescan 
  4. Resize your multipath device by running the multipathd resize command:
    # multipathd -k'resize map mpatha'
  5. Resize the filesystem (assuming no LVM or DOS partitions are used):
    # resize2fs /dev/mapper/mpatha

  Published under the terms of the Creative Commons License Design by Interspire