Third-party driver coexistence


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Third-party driver coexistence

The third-party driver (TPD) coexistence feature of VxVM 4.1 allows I/O that is controlled by third-party multipathing drivers to bypass DMP while retaining the monitoring capabilities of DMP. Provided that a suitable ASL is available, devices that use TPDs can be discovered without requiring you to set up a specification file, or to run a special command. In previous releases, VxVM only supported TPD coexistence if the code of the third-party driver was intrusively modified. The new TPD coexistence feature maintains backward compatibility with such methods, but it also permits coexistence without require any change in a third-party multipathing driver.

See Changing device naming for TPD-controlled enclosures for information on how to change the form of TPD device names that are displayed by VxVM.

See Displaying information about TPD-controlled devices for details of how to find out the TPD configuration information that is known to DMP.

Autodiscovery of EMC Symmetrix arrays

In VxVM 4.0, there were two possible ways to configure EMC Symmetrix arrays:

With EMC PowerPath installed, such devices could be configured as foreign devices as described in Adding foreign devices.
Without EMC PowerPath installed, DMP could be used to perform multipathing.

On upgrading a system to VxVM 4.1 or later release, existing EMC PowerPath devices can be discovered by DDL, and configured into DMP as autoconfigured disks with DMP nodes, even if PowerPath is being used to perform multipathing. There is no need to configure such arrays as foreign devices.

To use DMP with PowerPath, you should be aware of the following scenarios:

PowerPath	DMP	Array mode
Installed	The `libvxemc` ASL handles EMC arrays and DGC claiming internally. PowerPath handles failover. There is n o need to install the CxN00 ASL or APM.	Explicit failover.
Not installed; the array is not CxN00	DMP handles multipathing. The `libvxemc` ASL handles the EMC Symmetrix array.	Any.
Not installed; the array is CxN00	DMP handles multipathing. The CxN00 ASL and APM must be installed.	Any.

PowerPath

DMP

Array mode

Installed

The libvxemc ASL handles EMC arrays and DGC claiming internally. PowerPath handles failover.

There is n o need to install the CxN00 ASL or APM.

Explicit failover.

Not installed; the array is not CxN00

DMP handles multipathing.

The libvxemc ASL handles the EMC Symmetrix array.

Any.

Not installed; the array is CxN00

DMP handles multipathing.

The CxN00 ASL and APM must be installed.

Any.

Note If any EMCpower discs are configured as foreign discs, use the vxddladm rmforeign command to remove the foreign definitions, as shown in this example:

# vxddladm rmforeign blockpath=/dev/dsk/emcpower10 \ charpath=/dev/rdsk/emcpower10
To allow DMP to receive correct enquiry data, the Common Serial Number (C-bit) Symmetrix Director parameter must be set to enabled.


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