configuring 3PAR Multipathing in Windows

In case of SAN storage, most of the time we will be dealing with multipathing software to enable redundancy and load balancing of disks. The same is with 3PAR StoreServ.3PAR has HPDSMs for windows 2003 systems, but from windows 2008 onwards they are purely using native multipathing option to enable redundancy and load-balancing for SAN attached disks.

How to configure Native MPIO for Windows 2008 R2

Microsoft Multipath I/O (MPIO) is a Microsoft-provided framework and it is available as a native component in Windows 2008 and its latest releases. though MPIO is generic, it is not enabled by default and need to be installed and configured to serve the purpose it meant for.

follow below steps to install and configure Native MPIO on windows 2008 and its latest releases,

• Go to Control Panel. 
• Open Programs and Features.
• Select Turn on Windows Features.
• select MPIO and put a check and click install.

• After the installation of this component, reboot the server.
• once the server is up, configure MPIO.

To configure the MPIO:

• Go to Administrative Tools then click MPIO.
• Select Discover Multipath Tab.
• Click Add in the Middle where the Storage controller will be listed.

• select MPIO-ed Devices and the added Storage controller will be available.
• Close the box once everything is complete.

Linux Device Mapper Multipath

Device Mapper Multipath is included in the Linux operating system distributions. Device Mapper is an infrastructure in the Linux kernel. It provides a generic way to create virtual layers of block devices. It supports striping,mirroring, snapshots, concatenation, and multipathing. The multipath feature is provided with combination of DM Multipath kernel modules and multipath-tools user-space package.

How to check Disk Multipath in Linux,

Usage: multipath [-v level] [-d] [-l|-ll|-f|-F]
[-p failover|multibus|group_by_serial|group_by_prio]
[device]

Eg:-
[root@linux01:/root]# multipath -ll

mpath2 (360060e80046a310000006a3100000da9)
[size=34 GB][features="1 queue_if_no_path"][hwhandler="0"]
\_ round-robin 0 [active]
\_ 1:0:0:4 sdac 65:192 [active][ready]
\_ 0:0:0:4 sde 8:64 [active][ready]

mpath23 (360060e80046a310000006a3100000da6)
[size=34 GB][features="1 queue_if_no_path"][hwhandler="0"]
\_ round-robin 0 [active]
\_ 0:0:0:1 sdb 8:16 [active][ready]
\_ 1:0:0:1 sdz 65:144 [active][ready]

mpath1 (360060e80046a310000006a3100000da8)
[size=34 GB][features="1 queue_if_no_path"][hwhandler="0"]
\_ round-robin 0 [active]
\_ 1:0:0:3 sdab 65:176 [active][ready]
\_ 0:0:0:3 sdd 8:48 [active][ready]

mpath22 (360060e80046a310000006a3100000da5)
[size=34 GB][features="1 queue_if_no_path"][hwhandler="0"]
\_ round-robin 0 [active]
\_ 0:0:0:0 sda 8:0 [active][ready]
\_ 1:0:0:0 sdy 65:128 [active][ready]

Multipath Help file info
---------------------
Usage: multipath [-v level] [-d] [-l|-ll|-f|-F]
[-p failover|multibus|group_by_serial|group_by_prio]
[device]

-v level verbosity level

0 no output
1 print created devmap names only
2 default verbosity
3 print debug information
-b file bindings file location
-d dry run, do not create or update devmaps
-l show multipath topology (sysfs and DM info)
-ll show multipath topology (maximum info)
-f flush a multipath device map
-F flush all multipath device maps
-p policy force all maps to specified policy :
failover 1 path per priority group
multibus all paths in 1 priority group
group_by_serial 1 priority group per serial
group_by_prio 1 priority group per priority lvl
group_by_node_name 1 priority group per target node

device limit scope to the device's multipath
(udev-style $DEVNAME reference, eg /dev/sdb
or major:minor or a device map name)