Are VMWare Snapshots Good When Installing Patches?

We always snap our servers before we patch or do any maintenance on them. We also do a full backup with VEEAM in case the snapshot bites the dust.

In general yes, but there are some cases where snapshots can go wrong. E.g. in an AD environent. Restoring snapshots can cause AD corruption as the other servers and the rolled back ones do have different AD-databases.

http://www.virtualizationadmin.com/blogs/lowe/news/dont-snapshot-domain-controllers-96.html

Also if the snapshot of a client is quite old it could be kicked out of the domain after restoring the snapshot (but it an be joined back normally).

Asking this suggests, that you are unsure what the snapshot feature means. It means, you can rollback to a point in time completely, as if nothing that happened after that snapshot has ever happened. So yes, snapshots are certainly perfect for this.
Edit [as I see Andreas' comment right now] after 30 days, the computer's password is changed, so rolling can always mean to lose domain membership. Therefore, if you really plan to keep snapshots that long, you need to run a command right before the snapshot that changes the computer password, then, so that you have the full 30 days:
nltest.exe /sc_change_pwd:yourdomain.local

I'm going to say NO.

Performance is poor on a snapshot snapshots are evil.

I would recommend Full Backup or CLONE.

Not a snapshot and based on EE members questions on snapshots they don't understand them and get into snapshot hell.

Andreas, another thing: server 2012 introduced a different behavior when it comes to vm restoring, it is actually supported to restore snapshots:
http://blogs.msmvps.com/acefekay/2013/10/17/windows-server-2012-ad-cloning-snapshot-support-preventing-usn-rollbacks/ and https://technet.microsoft.com/en-us/library/virtual_active_directory_domain_controller_virtualization_hyperv%28v=ws.10%29.aspx?f=255&MSPPError=-2147217396 are good reads.

Andrew,

While I agree with you about how badly a snapshot can cause performance loss on a server, I have to disagree with your perspective. As long as you do what you need to do and then remove the snapshot and consolidate the disks if required you will not have any issues.

I'm just basing my evidence on EE questions Asked about Snapshots in the last five years and those that have corrupted failed VMs.

I strongly disagree on that. See here too.

http://www.vsysad.com/2012/12/dont-take-snapshots-of-a-domain-controller/

On 2012 and only on Hyper-V snapshots for an AD-Server are supported.

Besides this you may mess up things. There might be problems lurking that are not visible immediately but may cause havoc later.
Ive seen broken AD-forests due to snapshotting/imaging.

One thing you can do is to halt the other servers b4 you do the snapshot on the server you want to try out things, then let the others offline until the one with the snapshot is rolled back or confirmed working good.

After the others came back online do not revert the snapshot anymore.

It might work, it even might work without any issues, it might went will 1000times and in the 1001 time it might break.

"On 2012 and only on Hyper-V snapshots for an AD-Server are supported." - well that's what I said, right? No reason to call it "strongly disagree" if you actually agree.
I am not saying: hey let's do as many snapshots as possible on our DCs, no. Always be careful. I just felt the need to mention that 2012 was a game changer in that respect :)

I have to ask the question then... OP can you specify if you are using VMWare or Hyper-V?

If you are working on a DC then I would also have to recommend against snapshots as I should have specified in my earlier post I do this on servers that aren't redundant. There is no need to do this for your DC's as they would just fail over and continue operating as designed. Backups are always a highly recommended practice still.

Question is tagged VMware! But either hypervisor, or any hypervisor, the same applies!

My strongly disagree was pointed on Curts post. Not on your one.

Also jaxjags didnt mention what version of OS he want to snapshot and restore.
So my comments just aimed towards that its not ALWAYS a good idea to snap and restore as you like. It depends strongly on your situation.

For clients its in  very most cases okay. besides that fact of the changing machines passwords every 30 days and the drop from domain if restore of snapshot will be too old an the machines password already changed in the meantime.

But its indeed a great thing that 2012 now supporting snapshotting on Hyper-V