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Oracle® VM Server for SPARC 3.6 Administration Guide

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Updated: September 2019
 
 

Virtual Disk Back End Options

Different options can be specified when exporting a virtual disk back end. These options are indicated in the options= argument of the ldm add-vdsdev command as a comma-separated list. The valid options are: ro, slice, and excl.

Read-only (ro) Option

The read-only (ro) option specifies that the back end is to be exported as a read-only device. In that case, the virtual disk assigned to the guest domain can be accessed only for read operations, and any write operation to the virtual disk will fail.

Exclusive (excl) Option

The exclusive (excl) option specifies that the back end 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 back end is opened exclusively, it is not accessible by other applications in the service domain. This restriction prevents the applications running in the service domain from inadvertently using a back end that is also being used by a guest domain.


Note - Some drivers do not honor the excl option and will disallow some virtual disk back ends 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 might work with pseudo devices, such as disk volumes. If the driver of the back end does not honor the exclusive open, the back end excl option is ignored, and the back end is not opened exclusively.

    Because the excl option prevents applications running in the service domain from accessing a back end exported to a guest domain, do not set the excl option in the following situations:

  • When guest domains are running, if you want to be able to use commands such as format to manage physical disks, then do not export these disks with the excl option.

  • When you export a Solaris Volume Manager volume, such as a RAID or a mirrored volume, do not set the excl option. Otherwise, this can prevent Solaris Volume Manager from starting some recovery operation in case a component of the RAID or mirrored volume fails. See Using Virtual Disks With Solaris Volume Manager 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 back end multiple times from the same virtual disk service, see How to Export a Virtual Disk Back End Multiple Times for more information.

By default, the back end is opened non-exclusively. That way the back end still can be used by applications running in the service domain while it is exported to another domain.

Slice (slice) Option

A back end is normally exported either as a full disk or as a single-slice disk depending on its type. If the slice option is specified, then the back end is forcibly exported as a single-slice disk.

This option is useful when you want to export the raw content of a back end. For example, if you have a ZFS or Solaris Volume Manager volume where you have already stored data and you want your guest domain to access this data, then you should export the ZFS or Solaris Volume Manager volume using the slice option.

For more information about this option, see Virtual Disk Back End.