QSnap for ContinuousDataReplicator

Table of Contents


QSnap can be used with ContinuousDataReplicator on a source computer or a destination computer for several purposes. There are differences in its requirement and use, depending on the operating system, which are explained in some detail below.


QSnap can be optionally installed with CDR on Linux, on a destination computer, to perform the functions described below. In some cases this can provide better performance and functionality than using Logical Volume Management (LVM) to create File System Snapshots.

  • On a destination computer, QSnap can be used to create the snapshots that comprise a Recovery Point. By default, LVM is be used for this function instead of QSnap; for more information about LVM, refer to your Linux documentation.

For CDR on AIX, QSnap is not supported for these functions; refer to IBM documentation for more information about File System Snapshots created by LVM.

For CDR on HP-UX, QSnap is not supported for these functions.

QSnap can be installed with CDR on Solaris, on a destination computer, for configuring UFS and VxFS as CXBF devices.

QSnap for CDR on UNIX

By default, CDR on UNIX utilizes Logical Volume Management (LVM) for snapshot purposes, for the creation of Recovery Points on the destination computer. QSnap can be used for these purposes instead of LVM; to do so, you must install QSnap and configure CXBF devices.

Install QSnap

In addition to the CDR software, the QSnap software must be installed as well, on the destination computer(s). This can be done at the same time you install CDR, or separately.

Follow the steps below to change which snap engine will be used:

Before You Begin

  • Review Snapshot Engines - Support
  • In the source computer:
    • For Windows 2003 or higher, VSS is used as the default snap engine.
  • This procedure only applies to the destination computer.
  1. In the CommCell Browser, right-click the Replication Set on the source computer and select Properties.
  2. In the Replication Options tab, select one of the choices in the Select Snap Engine Type for Recovery Point Creation section.

    For Windows, VSS is the default selection; ONTAP can be used if available on the destination computer where the Recovery Point will be created.

    For UNIX, Snap Engine Type is automatically detected by the File System configured on the destination computer.

  3. Click OK to save your changes.

    On UNIX, CDR software automatically recognizes the File Systems configured on the destination computer and detects the appropriate snap engine. For more information on supported snap engines, see Snapshot Engines - Support.

Configure UNIX CXBF Devices for CDR

Before any volume can be used as a destination for CDR with QSnap on UNIX, it must be mounted and configured as a CXBF device using the procedure detailed here.

  1. Ensure that CDR and QSnap have been installed on the computer. For more information, see Deployment - ContinuousDataReplicator.
  2. Mount any volumes that will be used as a destination.
  3. Use Volume Explorer to configure CXBF devices for ContinuousDataReplicator.

    For CDR on Solaris, you have the option to configure CXBF devices during the creation of Replication Sets or Replication Pairs. This option applies to UFS and VxFS.

  4. Once you have configured destination volumes as CXBF devices, you can create Replication Sets and Replication Pairs that utilize those volumes.

    When selecting destination volumes for Replication Pairs, you must ensure that each volume you select is a CXBF device.

Deconfigure UNIX CXBF Devices used by CDR

If you no longer want to use a volume as a CXBF device for CDR, you can deconfigure it using Volume Explorer.