Snapshot In Windows and VMware

[H_Sharma]

Hello Experts,

My envornment is as below. Many VM machines and backup is happening via VMhost

Master:- Win 2008 Server with 7.6.0.1

Vcenter:- 5.5

1:- How does a snapshot is created in datastore in Vcenter. If vm's total size is 30 GB does it create 30 GB snapshot in Datastore? 

We have VSS included in our environment for Open file backup for physical clients that have netbackup client installed.

2:- How much space does the drive require for VSS. If I have 20 GB space and 10 GB is free. How much space does this snapshot require?

3:- What happens when full backup initiate does it take the total size of the disk? As i have found netbackup deletes the old snapshots when backup finishes.

So when incremental backup initiates where does it get the information to take the backup of changed blocks as old snapshot gets deleted?

Pls help.

[RiaanBadenhorst · Accepted solution]

Hello

I hope you're running the EEB because 5.5 is only supported on 7.6.0.1 +EEB EEB3318872

1. No it does not make a full size snapshot. This is more a vmware topic so look here for more information http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1025279
2. This is an MS topic so look here for more information http://msdn.microsoft.com/en-us/library/office/aa579091%28v=exchg.140%29.aspx
3. I dont understand what you mean with "does it take the total size of the disk". If you're referring to backing up.... NetBackup will backup all used blocks, not free blocks. So if the vmdk is 100GB and only 50 is used in the OS we'll backup 50.
4. Incremental rely on changed blocks. Check out this note http://www.symantec.com/business/support/index?page=content&id=HOWTO70912

[H_Sharma]

Hi Riaan,

Thanks for replying.

If .VMDK is created first time and its full backup will happen first time and if its used space is 40 GB out of 100 GB. It will create a 40 GB snapshot. Pls correct me if i am wrong.

[RiaanBadenhorst]

Hi Hargyan

Please take a look at this note

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1003755

It explains more about the snapshots and space required (look for the heading Virtual machine with snapshots). There you'll see that to create a snapshot without taking the virtual memory takes only a few hundred megabytes. This would grow depending on how  busy your server is as it has to keep all the changes written.

[Michael_G_Ander · Accepted solution]

1. Usually not, the snapshot contains the changed blocks since it was set. Size depends on time and activity

2.Same answer as 1.

3. Depends on your settings i the VMWARE policy, but in principle the full backup is reading all the blocks in the VM. Change block tracking if that has been set.

I would recommend that you study the Netbackup VMWARE manual, especially the section about reducing the VM backup sizes.