Enabling and Disabling Multipathing in the Solaris Operating System

This section describes how to enable and disable multipathing using the stmsboot(1M) administration program in the Solaris 10 10/08 operating system. The following subsections are included:

• About Multipathing

• stmsboot Options

• stmsboot Conditions

• To Enable Multipathing on LSI-Based Multipath-Capable Controllers

• To Disable Multipathing on LSI-Based Multipath-Capable Controllers

• Configuring Multipathing on Selected Ports

About Multipathing

Use the stmsboot command to enable multipathing in the Solaris. stmsboot manages enumeration of multipath–capable devices with multipathing and has these characteristics:

• Multipathing-enabled devices are enumerated under scsi_vhci(7D).

• Multipathing-disabled devices are enumerated under the physical controller.

After cabling your server for multipath, you will see two copies of each disk from the OS since you are using two separate array paths (SAS A and B). If you want to have multiple hosts accessing disks in the array, you must first set up zoning per host as described in Chapter 3, Adding and Zoning Array Storage Using CAM.

For example, if you have created a zone in each of the array's SAS domains that includes three disks, when entering the format command before MPxIO is installed, you will see two of each multipathed disk (zoned out disks that have not been assigned to a host will show as “unknown”). In this example, disk c1t1d0 is a system disk (not a J4500 array disk).

# format

AVAILABLE DISK SELECTIONS:
0. c1t1d0 <DEFAULT cyl 30397 alt 2 hd 255 sec 63>
 /pci@0,0/pci108e,534c@5/disk@1,0
1. c2t102d0 <DEFAULT cyl 17846 alt 2 hd 255 sec 63>
2. c2t111d0 <DEFAULT cyl 17846 alt 2 hd 255 sec 63>
/pci@0,0/pci10de,376@a/pci1000,3150@0/sd@66,04. c2t113d0 <DEFAULT cyl 17846 alt 2 hd 255 sec 63>
/pci@0,0/pci10de,376@a/pci1000,3150@0/sd@6f,0/pci@0,0/pci10de,376@a/pci1000,3150@0/sd@71,0
3. c2t112d0 <DEFAULT cyl 17846 alt 2 hd 255 sec 63>5. c2t118d0 <DEFAULT cyl 17846 alt 2 hd 255 sec 63>
/pci@0,0/pci10de,376@a/pci1000,3150@0/sd@70,06. c2t119d0 <DEFAULT cyl 17846 alt 2 hd 255 sec 63>/pci@0,0/pci10de,376@a/pci1000,3150@0/sd@76,0/pci@0,0/pci10de,376@a/pci1000,3150@0/sd@77,0
 
 
 
 
 
 
 

After installing MPxIO, entering the format command will show only three array disks. The J4500 array disks should have "scsi_vhci" in the path.

# format

AVAILABLE DISK SELECTIONS:
0. c1t1d0 <DEFAULT cyl 30397 alt 2 hd 255 sec 63>
 /pci@0,0/pci108e,534c@5/disk@1,0
1. c3t5000C500069E209Fd0 <DEFAULT cyl 17846 alt 2 hd 255 sec 63>
2. c3t5000C500069E1383d0 <DEFAULT cyl 17846 alt 2 hd 255 sec 63>
/scsi_vhci/disk@g5000c500069e209f
/scsi_vhci/disk@g5000c500069e1383
3. c3t5000C500069E2003d0 <DEFAULT cyl 17846 alt 2 hd 255 sec 63>
/scsi_vhci/disk@g5000c500069e2003
 
 

Details of the multipath disks may be obtained using the mpathadm command, as follows:

# mpathadm list lu

/dev/rdsk/c3t5000C500069E209Fd0s2
 Total Path Count: 2
/dev/rdsk/c3t5000C500069E2003d0s2
Operational Path Count: 2
Total Path Count: 2/dev/rdsk/c3t5000C500069E1383d0s2Operational Path Count: 2
Total Path Count: 2
Operational Path Count: 2
 
 
 
 

Device Renaming

In the /dev and /devices trees, multipathing-enabled devices receive new names that indicate that they are under multipathing control.

This means a device has a different name from its original name (after enabling) when it is under multipathing control.

The stmsboot command automatically updates /etc/vfstab and dump configuration to reflect the device names changes when enabling or disabling multipathing.

A reboot of the host server is required for changes to take effect.

Dynamic Discovery of SAS Devices

SAS devices, added and removed dynamically with the mpt(7d) driver, enable your system to detect specific targets and LUNs attached, with these conditions:

• If you add or remove a device in your SAS domain, messages are written to the /var/adm/messages file indicating presence or removal.

• If a device has been added, it is visible to, and available by, the format(1m) command.

stmsboot Options

The following table describes the options supported by stmsboot(1M).

Table 4-3 stmsboot Options for SAS Controllers

stmsboot Conditions

stmsboot enables and disables multipathing on the host, with these conditions:

• The utility automatically updates vfstab(4) and dumpadm(1M) configuration to reflect device-name changes.

  ---

  Note - The system administrator is responsible for modifying application configuration (for example, backup software, DBMS, and so forth) to reflect updated device names.

  ---

• The -L and -l options display the mapping between multipathed and non- multipathed device names, only after changes to the multipathing configuration take effect; that is, following reboot after invoking stmsboot -e.

• ZFS datasets, including ZFS root datasets, are correctly handled by stmsboot.

To Enable Multipathing on LSI-Based Multipath-Capable Controllers

• From the command prompt, enter the following command:

  # stmsboot -D mpt -e

  The following output is displayed (press y when prompted to accept the defaults).

  # stmsboot -D mpt -e
  WARNING: This operation will require a reboot.
  Do you want to continue ? [y/n] (default: y) y
  updating /platform/i86pc/boot_archive
  The changes will come into effect after rebooting the system.
  Reboot the system now ? [y/n] (default: y) y

  ---

  Note - stmsboot updates the /etc/vfstab file and dump configuration to reflect device-name changes during reboot.

  ---

  The following conditions apply to the stmsboot -e, -d, and -u options:

  • Reboot immediately after running stmsboot. If the following error occurs after rebooting, a second reboot is needed:

    ERROR: svc:/system/filesystem/root:default failed to mount /usr (see 'svcs -x' for details)

  • Ensure that eeprom(1m) boot device is set to boot from your current boot device; stmsboot reboots the machine to complete the operation.

  • stmsboot saves a copy of your original /kernel/drv/mpt.conf and /etc/vfstab files before modifying them.

To Disable Multipathing on LSI-Based Multipath-Capable Controllers

• From the command prompt, enter the following command:

  # stmsboot -D mpt -d

  The following output is an example of what might be displayed (press y when prompted to accept the defaults).

  # stmsboot -D mpt -d
  WARNING: This operation will require a reboot.
  Do you want to continue ? [y/n] (default: y) y
  The changes will come into effect after rebooting the system.
  Reboot the system now ? [y/n] (default: y) y

  ---

  Note - During reboot, /etc/vfstab and the dump configuration update to reflect the device-name changes.

  ---

Configuring Multipathing on Selected Ports

To enable multipathing on specific ports and disable multipathing on others, edit the /kernel/drv/mpt.conf file. To update vfstab(4) and dumpadm(1M) configurations to reflect the changed device names, type:

# stmsboot -u