Backup Exec 2010 R2 and Vsphere 4.1

[Brogan]

Good Day All

I am quite puzzeled by Backup Exec 2010 r2 backup of Vsphere 4.1 VM with VM agent. In the attached image the datastore is thick provisioned 1.14TB LUN from the SAN which has 2 vm's. The VM's are configured Thin Provisioned  As you can see the Capacity and Provisioned storage has about 400GB discrepency but that is only when backups are done as BE2010 processes snapshots. Here is the kicker, the backup is at 400GB but the free storage has not decreased i was expecting to run out of free space on the LUN but the backup is still processing and the servers are still up.

Can someone explain to me the BE2010 snapshot processing and the space needed to do snap shots from a BE2010 perspective.

[a_p_]

"Capacity" and "Free Space" are important. The provisioned disk space for a thin provisioned disk as well as snapshots equals the configured virtual disk size. Even though the snapshot only uses 100MB of physical disk space in your case, the provisioned size for the two snapshot disks is ~700GB.

André

[Shakaal]

Capacity Of Datastore is 1.14TB

Second Disk in VM is of size 512GB out of which around 432GB is being used
Size of the Snapshot for second disk is 24MB

first disk is of Size 160GB out of Which 155GB is being used
Size of the Snapshot for First Disk is 72MB

Total Snapshot size : 96MB

Total Capacity that is being used is 587GB for VM acs-da01

Free Space on DataStore is 324.95GB which can easily accomodate the Snapshot size

most of the backup software create snapshot of the VM's while taking Backup and will delete
the Snapshot once the backup job completes
The Size of the Snapshot depends upon the size of the Changes or I/O that have been made to the
VM or the Data on the VM's Disk.

Regards

[cjscol · Accepted solution]

The snapshot files will only contain the changes to the virtual machine while the backup is running.  When the backup starts it takes a snapshot of the virtual machines, this snapshot freezes the "main" virtual disk files.  New writes to the virtual disks will be written to the snapshot files, i.e. they only contain changes to the virtual machine.  The backup job is then safe to read from the "main" virtual disks knowing that they will not change and will be in the state of the virtual machine when the snapshot was taken.  Once the backup has finished it will "delete" the snapshot, this "merges" the changes in the "snapshot" files to the "main" virtual disk files.

So the "snapshot" files will only be as large as the amount of changes to the virtual disks while the snapshot is in place.  This has nothing to do with the amount of data backed up by Backup Exec as it reads from the "main" virtual disk files.

I guess you was expecting the "snapshot" files to grow the amount of data on the virtual disks and for Backup Exec to read from these snashot files.

I hope that makes sense.

[Brogan]

yes it makes alot of sense, I was under the impression the snapshot will be the same as the provisioned disk and be commited to physical disk and back exec will use the snapshot to make the backup, so i was thinking i was taking a chance by making snapshot backups which would fill up the available LUN space.

I clearly still have alot to learn: so in short snapshot of vm in be2010 is only used for when changes happen which are then written or commited to vm when backup is completed and in terms of capcity and free space planning the 325GB free space should be enough for growth purposes.

[a_p_]

In case you are interested in how snapshots work in VMware products, take a look at e.g. http://kb.vmware.com/kb/1015180

André

[Brogan]

thanks shakaal, andre and calvin