Specifications
Linux Configuration
Dynamic
device
addition
Prior to LifeKeeper startup, Linux must configure all devices. If a LifeKeeper
protected device is configured after LifeKeeper is started, LifeKeeper must be
stopped on each server that shares the device and then be restarted. This will
enable the device detection and validation to confirm the configuration and enable
LifeKeeper to access the device.
LUN
support
The Linux SCSI driver has several parameters that control which devices will be
probed for Logical Units (LUNs):
l List of devices thatdo notsupport 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.
l List of devices thatdosupport LUNs – this list of devices is known to
support LUNs well, so always probe for LUNs.
l 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"
SteelEye Protection Suite for Linux77