What are the VM size limitations for using NBD transport mode in VADP ?

[TomLambrechts]

We are having issue to perform VADP backup with EMC² Networker 7.6.2 with a VM which in total equals about 2.3 TB of data.
The setup is the following:

VM (fileserver) running on Windows 2008 R2

The backup server (physical) is running Networker 7.6.2 and is also proxy host for VADP backups.

VMware vSphere ESXi 4.1 Update 1

When we perform an ESX snapshot of the fileserver, no problem.
When we try a VADP backup via Networker, it fails with the following error:

Creating snapshot for 'vm-2153' ...

Task is -1% complete

Task is 95% complete

Task is 95% complete

Task is 95% complete

Task is 95% complete

74854:nsrvadp_save: The following VMware related error occured: Unable to create snapshot '_VADP-BACKUP_' for VM: vm-2153.  Details: 'An error occurred for task 'CreateSnapshot_Task'.  Details: Operation timed out.'.

80405:nsrvadp_save: Could not create Snapshot for VM 'PWVFILE05'.

Temporary directory 'V:\backupvmware\PWVFILE05' for VADP deleted.

Other client VADP backups (smaller ones) are running fine.

Someone told me that the NBD has certain limits regarding VM Size.
He said when he VM size equals 1TB or more, we should NOT use NBD.

Is anyone able to explain me or provide me with proof of this ?

[spravtek]

Hey Tom,

Check page 27 of this guide http://www.vmware.com/pdf/vsphere4/r40/vsp_vcb_15_u1_admin_guide.pdf

As well as this article: http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=101327...

They mention the 1TB limit, the KB also mentions what alternatives to use.

I hope this helps you along.

[TomLambrechts]

Yes ok, but that's about VCB and we are using VADP.
Are the limitations the same ?

[spravtek]

Hmmm good question, I'm no expert in backup, but isn't VADP using the NBD mode as well? I'll have to look into the fact if there are any differences though, can't be sure at the moment.

[edit, adding extra info]

Tom,

I found the PDF I was thinking about: http://pubs.vmware.com/vsphere-50/topic/com.vmware.ICbase/PDF/vddk_prog_guide.pdf

Page 23 still talks about the 1TB limit for NDB and virtual disks.

[TomLambrechts]

Ok, much appreciated.... Now we have it black on white 😉

so the best solution is going for SAN transport mode.
or we limit the disks to 1TB each.

[spravtek · Accepted solution]

Yeah, I think that's the best option, customers don't like "limits" very much, so maybe best look into the SAN transport mode

Good luck!

[TomLambrechts]

THX !

[DenisJannot]

Hi,  You can also uee the hotadd mode (the snapshot is attached to the proxy in this mode) if you set up a virtual proxy.  Best regards, Denis

[rash127]

Hi Dinis,

  HotAdd transport has 1TB limit of VMDK as well. The best choice for VMDK files larger than 1TB is SAN transport.

Warm regards,

Rasheed

Disclaimer: I work for Symantec. Comments are my own.

[DenisJannot]

Hi Rasheed,

Here is an extract of the Virtual Disk API Programming guide :

For LAN transport, virtual disks cannot be larger than 1TB each. As its name implies, this transport mode is not LAN-free, unlike SAN and HotAdd transport (http://pubs.vmware.com/vsphere-50/index.jsp?topic=/com.vmware.vddk.pg.doc_50/vddkPreface.html)

But,the block size chosen for the VMFS that holds the proxy is also important.

It must be 8MB to allow backing up a 2 TB virtual disk.

Best regards,

Denis