Article ID: 1963, created on Jun 20, 2007, last review on May 8, 2014

  • Applies to:
  • Virtuozzo containers for Windows 4.0


Shared loopback device is .efd file which emulates physical iSCSI or fiber channel SAN.

Create a VE and cluster it with another VE on the same server using a virtualized (simulated) iSCSI or fiber channel SAN. This configuration emulates the scenario when VEs are hosted on separate physical servers and facilitates a good environment for testing of applications in clustered servers.

To create a shared loopback disk please use the following command:

vzctl partadd VEID --drive d: --size 2000000 --file c:\vz\shareddrive\cluster.efd --shared --scsi

VEID - identification number of a VE the loopback disk is being added to.

 --size - specifies the size of loopback device in KB

 --file – specifies full path to file location. The file can either be local or reside on a SAN

 --shared – specifies that the loopback file will be shared by several VEs

 --scsi – specifies that the loopback device will behave as SCSI disk

Note: Using shared SCSI loopbacks without clustering software should be avoided since simultaneous mounting of the same disk in more than one VE may lead to file system corruption. Clustering software prevents corruption by means of IO filtering in the ClusDisk.sys driver.

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