cesarsj
Contributor
Contributor

I want to update the samba on a company production VM, only this VM is a 3 TB NAS. For security, would you have to make a backup only of the disk where the Linux root is?

We usually do clones instead of backup snapshots. Only in this case, as the NAS has 1 disk of 20 GB (where is Linux Root), and three disks of 1 TB where are the shared folders of the NAS, there is no storage in new vSphere that supports such space. Would taking a snapshot in this case be a good solution? I heard that snapshots are not the most suitable for backups. This backup would be to update the samba on the NAS, to, in case of errors, return to the functional version.

We have vSphere 6.7, and VM is an OS Slakcware 14.2. We like upgrade samba 4.4.16 to 4.6.16, to fix some security issues and also try to fix an error of multiple nobody connections coming from Windows 10 clients (not sure that the upgrade will solve the problem).

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7 Replies
daphnissov
Immortal
Immortal

Yes, this is an appropriate use of snapshots. I would say cloning any VM for operations like this (package/app updates) is way overkill and a waste of time and resources. Keep in mind that since this is a Slackware VM, you probably don't have the benefit of the file sync driver for quiescing snapshots. Be mindful, therefore, when you initiate the snapshot that you're most likely getting crash consistency.

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a_p_
Leadership
Leadership

You are right, snapshots are in no way comparable to backups. However, they are an excellent feature for what you are going to do, since this is not really a backup, but a way to return to the snapshot's state in case an update doesn't work as expected.

Since a VM snapshot will include all of the virtual disks (except that they are marked as "independent-persistent") you need to keep in mind that changes to the disks will be stored in additional .vmdk files which require additional disk space on the datastore.

André

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cesarsj
Contributor
Contributor

Keep in mind that since this is a Slackware VM, you probably don't have the benefit of the file sync driver for quiescing snapshots

I would like to understand this better, if you can explain it in more detail.

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daphnissov
Immortal
Immortal

When taking a snapshot, there is a box that asks you if you wish to quiesce the guest. Selecting this box will invoke the quiesce driver–in Linux it's the filesystem sync driver which is an optional install; in Windows it's VSS. If you do not check this box, the snapshot that is taken will be crash consistent–the buffers in memory will not be flushed to disk. Very often, especially for Linux guests, this is OK as there are abilities within the file system to reconcile those differences, but this is application specific. If you need 100% certainty that you have a known good snapshot, shut down the VM and take a cold snapshot. All snapshot revert actions done when the snapshot was taking without saving the memory state will return it to a powered off state anyhow. These are simply things to keep in mind whenever you snapshot a VM, for any purpose.

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cesarsj
Contributor
Contributor

Since a VM snapshot will include all of the virtual disks (except that they are marked as "independent-persistent") you need to keep in mind that changes to the disks will be stored in additional .vmdk files which require additional disk space on the datastore.

Is there a way for me to preview the disk size the snapshot will consume after it is done?

Another question I have is that if it is true that creating a snapshot consumes a lot of network resources while it is being done?

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cesarsj
Contributor
Contributor

So your tip is that I take the snapshot with the VM turned off, and in case the samba upgrade fails, it will be restored like this.

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daphnissov
Immortal
Immortal

Not necessarily. Samba isn't a transactional service like a database. You're probably fine taking it online but without the quiesce option checked. I'm simply stating for 100% security, which may be overkill, take the snapshot with the VM in a powered off state.

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