Oracle Solaris Storage Multipathing MPxIO provides multipath access to storage luns by grouping together the physical paths and presenting a single logical path. MPxIO can also be referred as STMS or SCSI_VHCI due to the commands used and logical device paths created.
For Solaris 10 and earlier
|/kernel/drv/fp.conf||Fiber channel port configuration file (For Fiber Channel Devices)|
|/kernel/drv/mpt.conf||mpt scsi/SAS HBA controller driver configuration file (For SAS Devices)|
|/kernel/drv/scsi_vhci.conf||MPXIO operation configuration file (Used to define loadbalancing and failback modes and configure 3rd party devices)|
|/kernel/drv/iscsi_conf||iSCSI MPxIO configuration file (For iSCSI devices)|
For Solaris 11
In case of Solaris 11, files in the directory /kernel/drv/ and /etc/driver/drv are the sample default configuration files delivered with OS (not used by MPxIO). Do not edit these files. The location of the configuration files is /etc/driver/drv/. The 4 configuration files used in case of Solaris 11 are the same, performing the same task. Although the syntax may be different.
/etc/driver/drv/fp.conf /etc/driver/drv/mpt.conf /etc/driver/drv/scsi_vhci.conf /etc/driver/drv/iscsi_conf
It is best practice to edit these files using the stmsboot utility, rather than editing them manually.
The syntax of the command stmsboot used to enable/disable MPxIO is :
stmsboot [-D fp|mpt] [-d | -e | -u | -L | -l controller_number] where: -D fp|mpt -> to select the protocol where you want to enable/disable mpxio -e -> to enable STMS on all HBA -d -> to disable STMS on all HBA -u -> to update vfstable and dump config after manual file configuration -l or -L unchanged - see the manpage of stms for a full description.
Few examples of using stmsboot command are :
|# stmsboot -e||To enable MPxIO or all devices (globally)|
|# stmsboot -D fp -e||To enable MPxIO for fiber channel devices|
|# stmsboot -d||To disable MPxIO for all devices (globally)|
How to confirm MPxIO is enabled
To make sure that MPxIO is enabled for a LUN, simply run the format command and check for the /scsi_vhci in the logical path of the LUN.
# format 4. c6t60060E800561CF00000061CF00000002d0 /scsi_vhci/ssd@g60060e800561cf00000061cf00000002
Another way is to check the “mpxio-disable” parameter in the configuration files :
# egrep "^mpxio-disable=" /kernel/drv/*.conf /kernel/drv/scsi_vhci.conf:mpxio-disable="no";
# egrep "^mpxio-disable=" /kernel/drv/*.conf /kernel/drv/fp.conf:mpxio-disable="no";
# egrep "^mpxio-disable=" /etc/driver/drv/*.conf /etc/driver/drv/fp.conf:mpxio-disable="no";
Verifying that the scsi_vhci module is loaded
scsi_vhci is the virtual host controller interconnect driver used to manage path of storage LUN. If you find that the scsi_vhci module is not loaded, then most likely MPxIO is not enabled.
Solaris[TM] 7,8,9,10,11 # modinfo -c |grep scsi_vhci 21 1 scsi_vhci LOADED/INSTALLED
Verifying Health of paths
We can check the multiple paths to the storage array LUNs by using mpathadm or luxadm command. The various states for the paths are :
ONLINE/primary ONLINE/secondary STANDBY/secondary OFFLINE/* UNAVAILABLE/*
mpathadm (supported for FC/SAS/iSCSI) [Works on Solaris 10, 11]
luxadm (supported on FC only) [Works on Solaris 7,8,9,10,11]
# mpathadm list LU /dev/rdsk/c9t60080E50001C0300000006464D8C9044d0s2 Total Path Count: 2 Operational Path Count: 2
To check the health of the paths using mpathadm :
# mpathadm show LU /dev/rdsk/c9t60080E50001C0300000006464D8C9044d0s2 Logical Unit: /dev/rdsk/c9t60080E50001C0300000006464D8C9044d0s2 mpath-support: libmpscsi_vhci.so Vendor: SUN Product: LCSM100_F Revision: 0777 Name Type: unknown type Name: 60080e50001c0300000006464d8c9044 Asymmetric: yes Current Load Balance: round-robin Logical Unit Group ID: NA Auto Failback: on Auto Probing: NA Paths: Initiator Port Name: 210000e08b07922c Target Port Name: 203d0080e51c2cc4 Override Path: NA Path State: OK Disabled: no Initiator Port Name: 210000e08b07f32c Target Port Name: 203e0080e51c2cc4 Override Path: NA Path State: OK Disabled: no .........
To check health of paths using luxadm :
# luxadm probe Found Fibre Channel device(s): ...... Logical Path:/dev/rdsk/c6t60060E800561CF00000061CF00000002d0s2 Node WWN:203e0080e51c2cc4 Device Type:Disk device ......
# luxadm display 203e0080e51c2cc4 DEVICE PROPERTIES for disk: 203e0080e51c2cc4 Vendor: SUN Product ID: LCSM100_F ------------> this is a 2540 or 2540-M2 array Revision: 0777 Serial Num: SV04720931 Unformatted capacity: 5120.000 MBytes Write Cache: Enabled Read Cache: Enabled Minimum prefetch: 0x3 Maximum prefetch: 0x0 Device Type: Disk device Path(s): /dev/rdsk/c9t60080E50001C0300000006464D8C9044d0s2 /devices/scsi_vhci/ssd@g60080e50001c0300000006464d8c9044:c,raw Controller /devices/pci@1d,700000/SUNW,qlc@1/fp@0,0 Device Address 203d0080e51c2cc4,0 Host controller port WWN 210000e08b07922c Class primary State ONLINE Controller /devices/pci@1c,600000/SUNW,qlc@1/fp@0,0 Device Address 203e0080e51c2cc4,0 Host controller port WWN 210000e08b07f32c Class secondary State ONLINE
Load Balancing policies
MPxIO also provides the load balancing capability to the I/O. There are basically 3 options to configure load balancing :
|Round Robin||Selects all paths in a round robin way.|
|Logical Block||I/Os within the range specified by range_size parameter would go on the same path. Improves performance on some storage arrays which have per path caching of data.|
|None||No load balancing – only one path is used.|
The load balancing policy can be set in the configuration file /kernel/drv/scsi_vhci.conf for solaris 10 and earlier or in the /etc/driver/drv/scsi_vhci.conf file for solaris 11.
Auto-failback policy enables the re-enable the failed path after it has recovered from the failure. By default the auto-failback is enabled. There are 2 ways to enable the auto-failback :
By this method, the auto-failback option does not persist across reboots.
# mpathadm modify mpath-support --autofailback on libmpscsi_vhci.so # mpathadm modify mpath-support -a on libmpscsi_vhci.so
For the changes to persist across reboots set the auto-failback parameter in the configuration file /kernel/drv/scsi_vhci.conf for solaris 10 and earlier or in the /etc/driver/drv/scsi_vhci.conf file for solaris 11. This requires a reconfiguration reboot.
To confirm that the auto-failback is enabled use :
# mpathadm show mpath-support libmpscsi_vhci.so | grep -i failback Supported Auto Failback Config: 1 Auto Failback: on <---<<< Failback Polling Rate (current/max): 0/0