Linux Configuration

Operating System

The default operating system must be installed to ensure that all required packages are installed. The minimal operating system install does not contain all of the required packages, and therefore, cannot be used with LifeKeeper.

Kernel updates

In order to provide the highest level of availability for a LifeKeeper cluster, the kernel version used on a system is very important.  The table below lists each supported distribution and version with the kernel that has passed LifeKeeper certification testing.

Note: Beginning with SPS v8.1, when performing a kernel upgrade on Red Hat Enterprise Linux and supported Red Hat Enterprise Linux derivatives (CentOS and OEL), it is no longer a requirement that the setup script (./setup) from the installation image be rerun. Modules should be automatically available to the upgraded kernel without any intervention as long as the kernel was installed from a proper Red Hat package (rpm file).
However, for Red Hat Enterprise Linux 7.3 or later and its compatible distributions, it may be necessary to update the kernel module. If DataKeeper fails to start after upgrading the kernel, check to see if the nbd kernel module is loaded. If it is not loaded run the SPS for Linux setup script to install the appropriate kernel module. There are no SPS kernel module requirements for SUSE Linux Enterprise Server.

 
Note:  This list of supported distributions and kernels is for LifeKeeper only. You should also determine and adhere to the supported distributions and kernels for your server and storage hardware as specified by the manufacturer.

LUN support

The Linux SCSI driver has several parameters that control which devices will be probed for Logical Units (LUNs):

• List of devices that do not support LUNs – this list of devices are known to NOT support LUNs, so the SCSI driver will not allow the probing of these devices for LUNs.

• List of devices that do support LUNs – this list of devices is known to support LUNs well, so always probe for LUNs.

• Probe all LUNs on each SCSI device – if a device is not found on either list, whether to probe or not.  This parameter is configured by make config in the SCSI module section.

While most distributions (including SUSE) have the Probe all LUNs setting enabled by default, Red Hat has the setting disabled by default.  External RAID controllers that are typically used in LifeKeeper configurations to protect data are frequently configured with multiple LUNs (Logical Units).  To enable LUN support, this field must be selected and the kernel remade.

To enable Probe all LUNs without rebuilding the kernel or modules, set the variable max_scsi_luns to 255 (which will cause the scan for up to 255 LUNs).  To set the max_scsi_luns on a kernel where the scsi driver is a module (e.g. Red Hat), add the following entry to /etc/modules.conf, rebuild the initial ramdisk and reboot loading that ramdisk:

   options scsi_mod max_scsi_luns=255

To set the max_scsi_luns on a kernel where the scsi driver is compiled into the kernel (e.g. SUSE), add the following entry to /etc/lilo.conf:

   append=“max_scsi_luns=255”

Note: For some devices, scanning for 255 LUNs can have an adverse effect on boot performance (in particular devices with the BLIST_SPARSELUN defined).  The Dell PV650F is an array where this has been experienced.  To avoid this performance problem, set the max_scsi_luns to the maximum number of LUNs you have configured on your arrays such as 16 or 32.  For example,

  append=“max_scsi_luns=16”

Testing environment of channel bonding, network teaming

In LifeKeeper, we performed tests in the environment using the channel bonding or network teaming with the following settings:

• Bonding policy in channel bonding

   + balance-rr

   + active-backup

• Runner in network teaming

   + round-robin

   + active-backup