QSnap for ContinuousDataReplicator

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Overview

• CDR on Windows
• CDR on UNIX

QSnap for CDR on UNIX

• Install QSnap
• Configure UNIX CXBF Devices for CDR
• Deconfigure UNIX CXBF Devices used by CDR

Overview

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. For CDR or QSnap installation procedures, refer to Deployment.

CDR on Windows

QSnap is always installed with CDR on either a source or destination computer, to perform the functions described below.

• On a source computer:
  • For Windows 2000, QSnap will be used to create a snapshot during the SmartSync Scan phase, to effect the transfer of the existing data to the destination computer.
  • For Windows 2003 and higher, VSS will be used to create a snapshot during the SmartSync Scan phase.
• On a destination computer, QSnap cannot be used to create Recovery Points, VSS is used for this function instead.

CDR on UNIX

QSnap can be optionally installed with CDR on Linux, on either a source or 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 source computer:
  • For Linux, QSnap can be used during the SmartSync Scan phase, to effect the transfer of the existing data to the destination computer. By default, LVM is be used for this function instead of QSnap; for more information about LVM, refer to your Linux documentation.
• 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.

QSnap for CDR on UNIX

By default, CDR on UNIX utilizes Logical Volume Management (LVM) for snapshot purposes, both during the SmartSync Scan phase on the source computer and 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 source and/or destination computer(s). This can be done at the same time you install CDR, or separately. For instructions, see Install QSnap - Unix.

To change which snap engine will be used, see Specify a Snap Engine.

Configure UNIX CXBF Devices for CDR

Before any volume can be used as a source or 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 procedures, see Install ContinuousDataReplicator - UNIX and Install QSnap - Unix.
2. Mount any volumes that will be used as a source or 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 source and/or destination volumes as CXBF devices, you can create Replication Sets and Replication Pairs that utilize those volumes.

   When selecting source and 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.

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