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HotAdd not working for VMs on other ESX host than Proxy

J
Byte
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Hi,

I’m currently experiencing issues with Hotadd backups using a VSA Proxy. The VMs running on the same ESX host as the Proxy are being backed up via Hotadd. However, VMs running on a different ESX host than the Proxy are being backed up via NBD.

As described in the Documentation: “If the virtual machine and the proxy are not on the same host, all datastores must be shared between the hosts and the hosts must be within the same datacenter. “

All datastores are shared between the hosts but they keep using NBD. I checked the logs and I can see Hotadd being disabled:

6452  1724  06/24 07:27:12 XXX CVMWareInfo::AdjustTransportModeForBackup() - Disabling Hotadd for VM [XXX] on NFS storage hosted by [XXX].  Proxy is hosted by [XXX]

What am I missing here?

Any ideas are appreciated!

Best answer by MichaelCapon

Hi @Jeremy,

 

By default we will use NBD instead of HotAdd when the VM and VSA are not on the same ESX Host. 

The reason for this is to avoid the symptoms of NFS locks that can occur with HotAdd, The issue is described here: https://kb.vmware.com/s/article/2010953

 

This behaviour is controllable with setting “SkipHotAddForNFSLock” documented here: https://documentation.commvault.com/additionalsetting/details?name=%22SkipHotAddForNFSLock%22&id=6866

 

Best Regards,

Michael

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3 replies

MichaelCapon
Vaulter
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  • MichaelCaponVaulter
  • Vaulter
  • 349 replies
  • Answer
  • June 26, 2023

Hi @Jeremy,

 

By default we will use NBD instead of HotAdd when the VM and VSA are not on the same ESX Host. 

The reason for this is to avoid the symptoms of NFS locks that can occur with HotAdd, The issue is described here: https://kb.vmware.com/s/article/2010953

 

This behaviour is controllable with setting “SkipHotAddForNFSLock” documented here: https://documentation.commvault.com/additionalsetting/details?name=%22SkipHotAddForNFSLock%22&id=6866

 

Best Regards,

Michael

J
Byte
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  • Jeremy
  • Author
  • Byte
  • 57 replies
  • June 26, 2023

Hi @MichaelCapon 

Thank you so much for your prompt reply.

As I understand it, it’s not ideal to use Hotadd in combination with NFS v3 datastores?

I read in the KB that NFS v4 is advised. If that’s not possible, NBD would still be advised in this instance? I’m wondering what the drawback would be to used NBD instead of Hotadd.

MichaelCapon
Vaulter
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Hi @Jeremy,

 

NBD is used in this scenario to ensure there is no impact to the VM’s due to the VM operations during the backup. 

Since NBD is transferring the data across the LAN (From ESX to VSA Proxy), you might see some lower throughput for that VM backup (depending on the network setup).

Another way around this (depending on the size of the environment) could be to deploy a VSA Proxy on each ESX Host to be used for the Backups.

 

Best Regards,

Michael

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