About VMWare Tools Quiescence for Linux guests

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About VMWare Tools Quiescence for Linux guests

Veeam Logoby antipolis » Thu Nov 24, 2016 9:39 am

Greetings,

I am quite confused about the "Enable VMWare Tools Quiescence" option.

We are backing up NFS Datastores stored on NetApp appliances, these datastores contain mixed Windows and Linux guests. Now on my initial implementation of Veeam I checked the "Enable VMWare Tools Quiescence" option, because according to the documentation https://helpcenter.veeam.com/docs/backup/vsphere/tools_quiescence.html?ver=95

To create transactionally consistent backups and replicas for VMs that do not support Microsoft VSS (for example, Linux VMs), you must enable VMware Tools quiescence for the job. In this case, Veeam Backup & Replication will use the VMware Tools to freeze the file system and application data on the VM before backup or replication.


Furthermore the text under the options says "only used for machines with application aware processing disabled". Most of our virtual machines DO have AA processing enabled with pre and post scripts for both windows and linux hosts, but I have a few linux hosts with cannot be processed by AA processing for all kinds of reasons ; so I figured ok let's enable quiescence so that "machines with application aware processing disabled" are processed by it

Now the Veeam Documentation (https://helpcenter.veeam.com/docs/backup/vsphere/tools_quiescence.html?ver=95) refers to this VMware article : https://pubs.vmware.com/vsphere-55/index.jsp?topic=%2Fcom.vmware.vddk.pg.doc%2FvddkBkupVadp.9.6.html

Which clearly states that "other guest operating system" (in the context of the article other = which is not windows) are "Not applicable" and does "Crash-consistent quiescing". I think back then VMWare had an experimental feature called the sync driver for linux operating systems, but it does not seem to be the case anymore, and as far as I'm aware sync is not included in the open-vm-tools package. Yes, we use OVT and not the official tools,this is the vmware recommendation : https://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2073803 :

VMware recommends using OVT redistributed by operating system vendors.


In the light of this, I don't see any upsides of enabling "VMWare Tools Quiescence" for our few non-AA linux guests, "crash consistent quiescing" does not appear very different to my than just backing it up straight away.

Furthermore, there is a lot of downsides for us for activating VMWare Tools Quiescence, from Veeam documentation :

https://helpcenter.veeam.com/docs/backup/vsphere/backup_from_storage_snapshots.html?ver=95

[For storage systems working over NFS] If you enable the Enable VMware tools quiescence option in the job settings, Veeam Backup & Replication will not use Backup from Storage Snapshots to process running Microsoft Windows VMs that have VMware Tools installed.


https://helpcenter.veeam.com/docs/backup/vsphere/direct_nfs_access.html?ver=95

If you enable the Enable VMware tools quiescence option in the job settings, Veeam Backup & Replication will not use the Direct NFS transport mode to process running Microsoft Windows VMs that have VMware Tools installed.


And yes, after some testing it appears that both backup from storage snapshot and directnfs are indeed not working for our windows VMs (which is counter intuitive because they have AA processing enabled)

To sum it up, my understanding of it (please correct me if I'm wrong, which was the motivation behind this post) is that in our case (just a few linux VMs without AA processing) enabling VMWare Tools Quiescence has no clear benefits and make us unable to use some veeam features (namely backup from storage snapshots and directnfs)

Sorry for the long post and thank you for your insight
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Re: About VMWare Tools Quiescence for Linux guests

Veeam Logoby PTide » Thu Nov 24, 2016 11:11 am

Hi,

Your understanding is correct. You should use Veeam AAIP settings for Microsoft VMs where possible. For all other VMs that are not suitable for Veeam default AAIP options (Linux VMs. MS VMs with custom software) you should specify pre-freeze and post-thaw scripts in the "Scripts" tab of the "Guest processing" settings.

Thanks.
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Re: About VMWare Tools Quiescence for Linux guests

Veeam Logoby antipolis » Thu Nov 24, 2016 11:35 am

Then I think the documentation should be updated, this page is misleading : https://helpcenter.veeam.com/docs/backup/vsphere/quiescence_choice.html?ver=95

You can enable both options for VM quiescence. Such scenario is recommended if you add Microsoft Windows and Linux VMs to the same job. In this case, all VMs will be processed in a transactionally consistent manner — either with application-aware processing or VMware Tools quiescence.


But this is not true for Linux VM because as mentionned in the VMWare article referred above VMWare Tools Quiescence will only be crash consistent for OS other than Windows (which makes this option kind of useless for Linux guests)
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Re: About VMWare Tools Quiescence for Linux guests

Veeam Logoby PTide » Thu Nov 24, 2016 1:56 pm

Then I think the documentation should be updated
We'll look into that, thanks!

But this is not true for Linux VM because as mentionned in the VMWare article referred above VMWare Tools Quiescence will only be crash consistent for OS other than Windows (which makes this option kind of useless for Linux guests)
As stated in the most recent VMware KB:

Quiesce: If the <quiesce> flag is 1 or true, and the virtual machine is powered on when the snapshot is taken, VMware Tools is used to quiesce the file system in the virtual machine. Quiescing a file system is a process of bringing the on-disk data of a physical or virtual computer into a state suitable for backups. This process might include such operations as flushing dirty buffers from the operating system's in-memory cache to disk, or other higher-level application-specific tasks.


On the other hand there is no mention what exactly does VMware quiescence do during snapshot regarding app-specific tasks. Previously it was possible to add custom pre-freeze and post-thaw sripts into specific directory (/usr/sbin/) so VMware Tools could trigger the scripts before and after a snaphost, however I haven't managed to find any info about that in the current VMware documentation. For now you should disable VMware native quiescence and use Veeam's pre-freeze/post-thaw scripts to make a consistent backup. I'll update the thread once I find out more details.

Thank you!
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Re: About VMWare Tools Quiescence for Linux guests

Veeam Logoby antipolis » Thu Nov 24, 2016 2:01 pm

Thank you for your feedback

PTide wrote: Previously it was possible to add custom pre-freeze and post-thaw sripts into specific directory (/usr/sbin/) so VMware Tools could trigger the scripts before and after a snaphost, however I haven't managed to find any info about that in the current VMware documentation.


From my own testing I was never able to make "native" /usr/sbin pre-freeze and post-thaw scripts work with either OVT (open-vm-tools) or official VMWare Tools so I am using the corresponding veeam options
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Re: About VMWare Tools Quiescence for Linux guests

Veeam Logoby DeWi » Thu Mar 16, 2017 11:35 am

Are there any news about this?
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Re: About VMWare Tools Quiescence for Linux guests

Veeam Logoby PTide » Thu Mar 16, 2017 7:10 pm

Hi,

The following steps should make it work:

1. Make sure that you have VMware tools installed
2. Create script /usr/sbin/pre-freeze-script
3. Make sure it has 0700 permissions and is owned by root:
Code: Select all
chmod 0700 /usr/sbin/pre-freeze-script
chown root /usr/sbin/pre-freeze-script

For post-thaw actions use a script named post-thaw-script.

Thanks
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[MERGED] Veeam & ensuring transactionally consistent workloa

Veeam Logoby rhys.hammond » Tue May 02, 2017 1:51 am

Hello Everyone!

Just hoping to run something by the Veeam team as I am after some clarification regarding application-consistent backups of Linux VMs.
So I thought transitionally consistent backups and 'proper backup and restore of VMs running highly transactional applications' are one the same.

https://helpcenter.veeam.com/docs/backup/vsphere/tools_quiescence.html?ver=95
"To create transactionally consistent backups and replicas for VMs that do not support VSS (for example, Linux VMs), you must enable VMware Tools quiescence for the job. In this case, Veeam Backup & Replication will use the VMware Tools to freeze the file system and application data on the VM before backup or replication."

Vs

https://helpcenter.veeam.com/docs/backup/vsphere/quiescence_choice.html?ver=95
'If you use VMware Tools quiescence, Veeam Backup & Replication will quiesce the VM but will not perform application-specific actions required for proper backup and restore of VMs running highly transactional applications.'

It's been discussed in other threads with mention of looking into the help guide and updating it here, https://forums.veeam.com/vmware-vsphere-f24/about-vmware-tools-quiescence-for-linux-guests-t39069.html.

In my mind, we should always be using the pre-freeze and post-thaw scripts to ensure application consistency and never relying on 'enabling VMware Tools Quiescence'.
http://rhyshammond.com - unofficial vmce v9.5 practice exam
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Re: About VMWare Tools Quiescence for Linux guests

Veeam Logoby DGrinev » Tue May 02, 2017 4:59 pm 1 person likes this post

Hi Rhys,

Yes, you're right as best practice states to use pre-freeze/post-thaw scripts, for the rest information please check discussion above.

Thanks!
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