System Center 2012 SP1 – DPM has enabled data protection for Windows 2012 Private Cloud deployments. Customers have been looking for a way to exclude some of the VHD/VHDX that have temp data or downloads or page files which have no value @ recovery time. Based on this feedback, we have introduced a new feature called “exclude VHDX”, where customer can configure DPM to exclude some of the VHDs on their backup. All backup admin has to do is run the following command on DPM server.
PS C:\> Set-DPMGlobalProperty -DPMServerName TestingServer -HyperVPagefileExclusions "*Temp.vhd"
By issuing this command, DPM excludes any file name that ends with “Temp.VHD” in the Delta Replication (DR). Since these files are included in the VM configuration and Hyper-V expects these files to be there for successful VM start, DPM copies these files for the first time and excludes in subsequent DRs. At the time of recovery, DPM will recover the “excluded” files as well. This will ensure that the Hyper-V is able to run VM successfully.
This command can take wild cards and multiple names. For ex., "*_pagefile.vhd,*mynotuseful*.vhd*" excludes backup of any vhd/vhdx that has word “mynotuseful” in their names and VHD file name that ends with “_pagefile.vhd”. Note that the file name strings are case insensitive. This command applies to all VMs protected by this DPM server. If there are multiple DPM servers present in the environment, this command needs to be run on each DPM server. One important aspect to consider at the VM deployment is pagefile size increases and its impact on VHD size. While Hyper-V allows changes to VHD file size after initial creation, it is advised to plan for VHD size at initial time itself. DPM backs up VHD only in the beginning and any subsequent changes in the VHD will not be backed up and could lead to issues at the time of VM recovery.
If this feature is enabled on the DPM server that has VMs being protected already, DPM will stop backing up the “exclude VHDs” in subsequent backups.
One of the biggest disk churning that has no value for customer @ recovery time is page file. Using this “exclude VHDs” feature, customer can remove the page file changes in the DPM backups. Here are the steps involved in excluding pagefile in backup.
1) Add a new VHD say “TempVHD” to the VM
2) Start the VM
3) Format the TempVHD disk and configure it to a drive letter say “E:\”
4) Move the pagefile to E:\
5) Run Set-DPMGlobalProperty -DPMServerName TestingServer -HyperVPagefileExclusions "Temp.vhd" on DPM Server
Once these steps are done, DPM will copy whole TempVHD as part of Initial Replication (IR) and will be excluded in subsequent DRs. If DPM goes through a CC or VM file spec changes, TempVHD will be copied in full and subsequent DRs will be skipped.
Our research found that, even though VM is churning at 10% of VM size a day, only 30% to 40% of this churning is due to the actual application data that is important to customer at recovery time but rest of the churning due to pagefile changes and temp file changes that has no use for customer at recovery time. In these kinds of environments, DPM 2012 SP1 brings in huge backup storage and network bandwidth savings. While actual storage savings vary depending on the environment, consider the following Windows 2012 64 node cluster with 4,000 VMs deployment.
Here is the storage consumption comparison between DPM 2012 and DPM 2012 SP1.
While the above example refers to Hyper-V CSV cluster, this feature works with all kinds of Hyper-V deployments that are protected by DPM 2012 SP1. Here are the list of deployments that are supported by DPM 2012 SP1.
1) Windows 2012 Hyper-V standalone
2) Windows 2012 Hyper-V CSV cluster
3) Windows 2012 Hyper-V standalone with remote Windows SMB file server (standalone or cluster)
4) Windows 2012 Hyper-V cluster with remote Windows SMB file server (standalone or cluster)
5) Windows 2008 R2 standalone
6) Windows 2008 R2 CSV cluster
As described in the TechNet article, Exclude VHD names can be added, removed or extended. Following command can be used to find out the current exclusions.
PS C:\> Get-DPMGlobalProperty –PropertyName HyperVPagefileExclusions
Note that, this is a DPM Global Property and so the values can be “set” only. So if additions or deletions to be done, first get the global property, modify string pattern, and then set the property again.