does backup write new data to virtual machine during snapshot

That is to do with the VSS Shadow Copy which Netbackup uses in the OS Partition.

I have seen some VMs run out of space during snapshot, but I am not sure if it is caused by Backup software, never heard of it before.

Yes it happens with NetBackup.

this is not to be confused with the VMware Snapshot on the dataastore, wich can also run out of datastore space.

This is INTERNALL in the VM - yes it happenes, and VMs then restart and crash!

this is not to be confused with the VMware Snapshot on the dataastore, wich can also run out of datastore space

.

I believe that is what it is per the VMware Adminstrator..
But I am not sure if the Netbackup writes new Data to the VM

Netbackup whilst backing up a VMware VM, the result can fill up the VM disk space, internally in the VM, and crash VMs, it happens here....

that is writing new data to the VM

so YES

e.g. it was not there before the backup, it is now, when it backups it up, runs out of space, VM restarts...

wonder what kind of data it writes...

I have other VMs in the same Datastore as the VM that crashed.. but other VMs did Not run out of space and crashed.

I was waiting for that question, and I'm going to have to refer you to the Vendor for NetBackup for that.....

Volume Shadow Copy fills up disk space.....

and ask that very question, because the last time we asked that question of NetBackup, we got a load of foo

As you can tell they are one of our favorite backup vendors - NOT

(that's a joke, if it didn't translate from British Speak!)

Andrew,

when  you say, the Datastore run out of space.. should not other VMs on the same Datastore also run out of disk space. ?

On the Edit Settings of the VM, I see:
VM disk  is Thin Provisioned , provisioned size : 60GB  ---Maximum Size : 300 GB
 so the VM disk will fill up till it reaches 300GB , if that space is available on the Datastore.


** let 's say Datastore has 200 GB
 if they set up Maximum Size to 300 GB, will VMware system warn the Administrator that the Datastore the VM is on does  not have that  much space ? or they can put any number on the Maximum Size field, and Vmware system will not care ?

Thanks

your recent posting, is nothing to do with your original question. It's off topic, please try to keep your questions on topic, muddling the question.
 
A reminder of your original question:-

does backup write new data to virtual machine during snapshot

I believe this question has been answered, please select a solution, and award points.

Please post a new question, on your recent posting and myself or other experts will be glad to assist.

No Problem
Thank you