Contents
Abstract
Linux multipathing provides IO failover and path load sharing for
multipathed block devices. The multipath IO support in SUSEŽ Linux Enterprise Server is based on
the Device Mapper multipath module of the Linux kernel and the
multipath-tools
userspace package.
Device mapping multipath IO features automatic configuration of the subsystem for a large variety of setups. Active/passive or active/active (with round-robin load balancing) configurations of up to eight paths to each device are supported.
multipath-tools
take care of automatic path
discovery and grouping as well as automated path retesting, so that a
previously failed path is automatically reinstated when it becomes healthy
again. This minimizes the need for administrator attention in a production
environment.
Device mapping multipath IO supports partitions (with limitations) and
LVM2. Software RAID is also supported, but automatic discovery is not
available.
To use software RAID with mdadm, /etc/mdadm.conf
must be
set up correctly. See Section 10.4, “Using the Devices” for more information.
Currently, device mapping multipath IO is not available for the boot partition, because the boot loader cannot handle multipath IO. Therefore it is recommended to set up a separate boot partition when using multipath IO.
Multipath IO is available on all platforms supported by SUSE Linux Enterprise Server. The following storage subsystems are detected automatically:
3Pardata VV
Compaq HSV110 / MSA1000
DDN SAN MultiDirector
DEC HSG80
EMC CLARiiON CX
FSC CentricStor
HP HSV110 / A6189A / Open-
Hitachi DF400 / DF500 / DF600
IBM 3542 / ProFibre 4000R / F20 / SVC / DS6000 / DS8000
NETAPP
SGI TP9100 / TP9300 / TP9400 / TP9500
STK OPENstorage DS280
SUN StorEdge 3510 / T4
Most other storage subsystems should work, but require manual
configuration in /etc/multipath.conf
.
Storage subsystems that require special commands on failover from one path to the other or require special nonstandard error handling might require more extensive support. Therefore the DM framework has hooks for hardware handlers and one such handler for the EMC CLARiiON CX family of arrays is already provided.