Linux host attachment overview

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IBM® supports the two largest commercial Linux® distributions, Red Hat Enterprise Linux (RHEL) and SUSE Linux Enterprise Server (SLES). You can apply this information, in general, to other Linux distributions.

IBM supports various host bus adapters (HBAs) manufactured by Marvell QLogic and Broadcom Emulex. These guidelines assume that the HBA was previously installed. For all newer versions of RHEL and SLES, use the Linux multipathing driver, Device-Mapper Multipath (DM Multipath). This section assumes DM Multipath is used. Use the HBA driver that is included with the distribution.

The procedures for attaching DS8000® storage are similar to the procedures for attaching most storage systems to Linux. There might be more than one way to complete each procedure. For more information about configuring storage on your specific Linux distribution, see your distribution documentation. For example, detailed information for Red Hat is provided in the Storage Administration Guide, which is included in the Red Hat documentation.

Adding LUNs to a Linux host
To add DS8000 LUNs to a Linux host, complete the following steps.
  1. Configure multipathing.
  2. Scan for new LUNs.
  3. Ensure that the LUNs are discovered and multipathed correctly.
  4. Partition, format, and mount the multipathed devices, as needed.
For more information, see your Linux distribution documents.
Locating the WWPN for a Linux host
You can use several methods to locate the worldwide port names (WWPN) for a Linux host, however the simplest is the systool utility, which is included in the sysfsutil package.

To locate one or more WWPNs, enter the following command:

# systool -c fc_host -A "port_name"

Configuring Device-Mapper Multipath for a Linux host
Device-Mapper Multipath (DM Multipath) is the preferred multipathing method on Red Hat Enterprise Linux and SUSE Linux Enterprise Server.

For multipathing on Red Hat Enterprise Linux, use the defaults that are compiled into DM Multipath.

multipath.conf is a user-configurable file. The recommended settings are baseline recommendations and can be modified as needed.

Managing SCSI disk connectivity on a Linux host
To scan for new LUNs on RHEL/SLES, complete the following steps:
  1. Upgrade the HBA driver to the latest stable version.
  2. Install or upgrade sg3_utils-*.rpm to the latest version on RHEL/SLES.
  3. Install or upgrade scsi-*.rpm to the latest version on SLES.
  4. Ensure that the Device Mapper Multipath (DMMP) tool is enabled.
  5. Enter sh rescan-scsi-bus.sh -r.
  6. Enter multipath.
  7. Enter multipath -ll.
    Note: The format of the command string is lowercase "ll".

    This adds any new LUNs to the configuration. No reboot is required.

To expand or shrink the LUN size on RHEL/SLES and above, complete the following steps:
  1. Upgrade the HBA driver to the latest stable version.
  2. Install or upgrade sg3_utils-*.rpm to the latest version on RHEL/SLES.
  3. Install or upgrade scsi-*.rpm to the latest version on SLES.
  4. Ensure that the Device Mapper Multipath (DMMP) tool is enabled.
  5. Ensure that the LUNs that you want to expand or shrink are not mounted or in use by other applications.
  6. Enter sh rescan-scsi-bus.sh -r
  7. Enter multipath -F.
  8. Enter multipath.
  9. Enter multipath -ll.
    Note: The format of the command string is lowercase "ll".

    This expands or shrinks the LUN size. No reboot is required.

For more information, see your Linux distribution documentation.