The exclusive (excl) option specifies that the backend in the service domain has to be opened exclusively by the virtual disk server when it is exported as a virtual disk to another domain. When a backend is opened exclusively, it is not accessible by other applications in the service domain. This prevents the applications running in the service domain from inadvertently using a backend that is also being used by a guest domain.
Some drivers do not honor the excl option and will disallow some virtual disk backends from being opened exclusively. The excl option is known to work with physical disks and slices, but the option does not work with files. It may or may not work with pseudo devices, such as disk volumes. If the driver of the backend does not honor the exclusive open, the backend excl option is ignored, and the backend is not opened exclusively.
Because the excl option prevents applications running in the service domain from accessing a backend exported to a guest domain, do not set the excl option in the following situations:
When you export an SVM volume, such as a RAID or a mirrored volume, do not set the excl option. Otherwise, this can prevent SVM from starting some recovery operation in case a component of the RAID or mirrored volume fails. See Using Virtual Disks on Top of SVM for more information.
If the Veritas Volume Manager (VxVM) is installed in the service domain and Veritas Dynamic Multipathing (VxDMP) is enabled for physical disks, then physical disks have to be exported without the (non-default) excl option. Otherwise, the export fails, because the virtual disk server (vds) is unable to open the physical disk device. See Using Virtual Disks When VxVM Is Installed for more information.
If you are exporting the same virtual disk backend multiple times from the same virtual disk service, see Export a Virtual Disk Backend Multiple Times for more information.
By default, the backend is opened non-exclusively. That way the backend still can be used by applications running in the service domain while it is exported to another domain. Note that this is a new behavior starting with the Solaris 10 5/08 OS release. Prior to the Solaris 10 5/08 OS release, disk backends were always opened exclusively, and it was not possible to have a backend opened non-exclusively.