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Avoiding replication of paging files and other transient data in Site Recovery Manager (2009324)

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While vCenter Site Recovery Manager (SRM) allows you to replicate transient data, such as Windows paging files or virtual machine swapfiles, such data need not be replicated. You may want to prevent replication of such data to avoid unnecessary consumption of network bandwidth and also in cases when storage vendors recommend it with some forms of replication.
You can configure protected virtual machines to use local (nonreplicated) storage for swapfiles, Windows paging files, or both.
This article provides steps to:
  • Specify a nonreplicated datastore for swapfiles
  • Create a nonreplicated virtual disk for paging file storage


Specifying a nonreplicated datastore for swapfiles

Every virtual machine requires a swapfile, which is normally created in the same datastore as the other virtual machine files. When you use SRM, this datastore is replicated. To prevent swapfiles from being replicated, create them on a nonreplicated datastore.
Note: If you are using a nonreplicated datastore for swapfiles, you must create a nonreplicated datastore for all protected clusters at both the protected and recovery sites. For more information, see the vSphere documentation.
To specify a nonreplicated datastore for swap files:
  1. In the vSphere Client, right-click an ESX/ESXi cluster and click Edit Settings.
  2. In the Settings window for the cluster, click Swapfile Location, select Store the swapfile in the datastore specified by the host, and then click OK.
  3. For each host in the cluster, select a nonreplicated datastore.

    1. Click the Configuration tab.
    2. On the Swapfile Location line, click Edit.
    3. In the Virtual Machine Swapfile Location window, select a nonreplicated datastore and click OK.

Creating a nonreplicated virtual disk for paging file storage

You can avoid replication of a virtual machine's Windows paging file by creating a virtual disk on a nonreplicated datastore, configuring Windows to create its paging file on that disk, and configuring a nonreplicated copy of that disk at the recovery site.

In the default configuration, Windows creates its paging file on the system disk (typically C:). Paging files created on this disk are always replicated when the virtual machine uses a replicated datastore. You can configure any virtual machine to use a virtual disk on a nonreplicated datastore for its paging file. SRM detects that the virtual machine depends on a nonreplicated virtual disk (the paging file disk) and removes that virtual machine from its protection group until you make a copy of that virtual disk file at the recovery site for the recovered virtual machine to use.
Note: To simplify creating a nonreplicated virtual disk for every virtual machine in a protection group, you can create a virtual disk file template and then clone it.
To create a nonreplicated virtual disk for paging file storage:
  1. At the protected site, select a nonessential virtual machine (one that you can power off during this procedure) or create a temporary virtual machine for this purpose.

    Because of differences in the NTFS file system among Windows releases, you must perform this procedure for each version of Windows that the protection group includes.

  2. Power off the selected virtual machine and add a new disk to it.

    Create the disk file on a nonreplicated datastore at the protected site in a location where you typically store virtual machine templates. This disk becomes the template for all nonreplicated paging file disks. Create it with adequate capacity for a typical Windows paging file.

  3. Power on the selected virtual machine and then create and format a partition on the new disk.
  4. Configure the virtual machine to create its paging file on the new disk.
  5. Power off the virtual machine and disconnect the new disk from it.

    You can clone this disk to provide nonreplicated paging file storage for the other virtual machines.

  6. To make the template available for cloning at the recovery site, copy it to a folder in a nonreplicated datastore at the recovery site.

    You must copy the .vmdk file and its flat counterpart, for example, pagedisk.vmdk and pagediskflat.vmdk.

  7. At the recovery site, use the vmkfstools command to create a clone of the copied disk.

    Create one clone for every placeholder virtual machine, but do not attach any clones to a virtual machine. The clones are assigned as part of the protection configuration process and are attached during recovery.

  8. At the protected site, configure each protected virtual machine.

    1. Use the vmkfstools command to clone the disk.

      Create the clone on a nonreplicated datastore at the protected site, and then copy it to a nonreplicated datastore at the recovery site with the original .vmdk file.

    2. Connect the cloned disk to the virtual machine and then power on the virtual machine and assign a drive to the cloned disk.
    3. Configure the virtual machine to create its paging file on the cloned disk.
    4. Power off and then power on the virtual machine, so that it writes its paging file to the new location on the cloned disk.

      At this point, the protected virtual machine is writing its paging file to a disk on a nonreplicated datastore at the protected site. Until you specify a recovery site location for this disk, the virtual machine does not have a valid protection configuration.

    5. Assign recovery site storage for the paging file disk to one of the clones that you copied from the protected site. For more information, see the Configure Protection for a Virtual Machine or Template section of the VMware vCenter Site Recovery Manager 5.8 Administration Guide.

      Initially, the paging file disk has a Recovery Location that is Not Configured. Click Browse, and then browse to the cloned vmdk file at the recovery site.

After you have configured the virtual machine to use the nonreplicated disk at the recovery site, SRM considers the virtual machine’s storage as properly configured and returns it to the protection group.

Additional Information

VMware is aware of an issue in SRM 5.8.0 and later releases where the methods described above fails. Currently, there is no resolution for this issue. This issue occurs if  a top-level file in a datastore is specified as a recovery for a non-replicated swap disk on the protected site. In prior releases this would work, but in SRM 5.8 and later, when this occurs you see a message similar to:

Failed to resolve file locator for backing of device 2001: (dr.storageProvider.fault.ResolvedVmFileNotFound)

For SRM 5.8.0, the workaround is to make a top-level folder for swap files and then specify the path for the each of the protected and recovery swap files for this virtual machine with this folder name prepended. For example, use:
[DSS_DRLinuxSwap] folder1/ITROMSPV11_SWAP.vmdk
instead of:
[DSS_DRLinuxSwap] ITROMSPV11_SWAP.vmdk
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Update History

01/14/2015 - Added SRM 5.8 to Products

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