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The scsi_vhci driver is a SCSA compliant
pseudo nexus driver that supports multipath services for fibre channel attached
SCSI-3 devices. This driver introduces a fundamental restructuring of the
Solaris device tree to enable a multipath device to be represented as single
device instance rather than as an instance per physical path as in earlier
Solaris versions.
The multipath SCSI target devices managed by this driver are identified
and represented by using SCSI-3 VPD page (0x83) as the device's unit address.
Symbolic links in /dev/[r]dsk continue to adhere
to the cNtNdNsN format. cN
is the logical controller number assigned to this driver instance. tN is the global unique identifier (GUID) of the multipath target
device (64/128 bits), represented as hexadecimal numbers.
The following is an example of a system with a A5000 storage array:
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...
/dev/rdsk/c4t200000203709C3F5d0s0 -> ../../devices/scsi_vhci/
ssd@g200000203709c3f5:a,raw
...
/dev/rdsk/c4t200000203709C3F5d0s7 -> ../../devices/scsi_vhci/
ssd@g200000203709c3f5:h,ra
...
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The following is an example of a system with a T300 storage array:
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...
/dev/rdsk/c1t60020F200000033939C2C2B60008D4AEd0s0 -> ../../devices/
scsi_vhci/ssd@g60020f200000033939a2c2b60008d4ae:a,raw
...
/dev/rdsk/c1t60020F200000033939A2C2B60008D4AEd0s7 -> ../../devices/
scsi_vhci/ssd@g60020f200000033939a2c2b60008d4ae:h,raw
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The scsi_vhci driver receives naming and transport
services from one or more physical HBA devices. To support multi-pathing,
a physical HBA driver must comply with the multipathing services provided
by this driver. Currently, the fcp(7D) fibre channel
SCSI protocol driver is the only driver to comply with the services provided
by the scsi_vhci driver.
Note – Enabling this feature on an upgraded implementation may result
in a new naming scheme for multipath devices under /dev
and /devices. If this happens, older links will be invalid
and existing file systems will be unusable.The scsi_vhci driver supports the standard functions
provided by the SCSA interface.
CONFIGURATION
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The scsi_vhci driver can be configured by defining
properties in the scsi_vhci.conf file. The scsi_vhci.conf file overrides the default settings. (See driver.conf(4)).
The scsi_vhci driver supports the following properties:
| PROPERTY NAME | DEFAULT | POSSIBLE VALUES |
| mpxio-disable | no | yes or no |
| load-balance | round robin | none or round-robin |
The mpxio-disable property determines if the HBA
driver instance is attached to the mpxio framework. By
default, HBA drivers register themselves with the mpxio
framework. If the mpxio-disable property is set to value "yes,"
the device tree space continues to work in the current way, that is, SCSI
target devices are created under the physical parent node. The mpxio-disable property comprises a system wide enable/disable. To
coexist with other multipath solutions, certain SCSI HBA drivers must enable/disable
the mpxio functionality on a HBA instance basis. The HBA
driver implementation manages this using properties configurable through the driver.conf file. Please refer to the corresponding HBA driver
man page for information on how to disable mpxio on a HBA
driver instance basis.
By default, the load balance property is ON. You
can globally disable it by setting the load balance string
property to "none" through the driver.conf
file. The scsi_vhci driver supports a simple round robin
automatic path selection model.
Setting load balance to "round-robin"
enables paths in ONLINE state to be selected for I/O in a round robin fashion.
A sample configuration file follows:
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...
# mpxio Global enable/disable configuration
# possible values are mpxio-disable="no" or mpxio-disable="yes"
#
mpxio-disable="no";
#
# Load Balancing global configuration
# possible values are load-balance="none" or load-balance="round-robin"
#
load-balance="round-robin";
#
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Sample prtconf(1M)
(verbose option) output of scsi_vhci properties is shown
below:
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scsi_vhci, instance #0
System properties:
...
name <mpxio disable> length <3>
value 'no'
name <load balance> length <12>
value 'round-robin'
...
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