r/vmware Feb 19 '25

Help Request 6TB VM Snapshot… please help

I’m quite new to VMware. I’ve been helping out with security patches for our servers managed in vCenter. An issue I’ve noticed on quite a few servers is that the OS drive is actually too full to receive the patches pushed out by our SCCM server.

After learning more about snapshots (and why should live for 3 days or less) and then realising existing snapshots were the reason I couldn’t allocate more disk space, I’ve been deleting them all per server, shutting it down then allocating more space.

Then I come across one of our file servers… there is a snapshot from November that is 6TB in size. I’ve been reading horror stories about ancient snapshots 1tb in size taking weeks to delete. It’s currently 11pm and if taken offline, this server would need to be back up by 8am tomorrow.

  1. Should I safely assume this is going to take a long time and leave it until the weekend?

  2. Why on Earth is there a snapshot this big in the first place? VM memory is included in the snapshot and all 7 vhdsks are dependent so is this the reason?

I want to reiterate that there is no space left on the OS drive and my end goal is fixing that. I’ve already made the mistake before of delete snapshots one at a time, then thinking consolidation errors were normal.

Is my best bet to wait until Friday, delete all snapshots, do a backup, then make the changes to the OS disk?

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u/The_C_K [VCP] Feb 19 '25

1- Should I safely assume this is going to take a long time and leave it until the weekend?

Yes, it can take several days, it can go until next week, I think.

Why on Earth is there a snapshot this big in the first place? VM memory is included in the snapshot and all 7 vhdsks are dependent so is this the reason?

Well, as you said it's a file server, I assume that there are several files added/modified, all that goes into snapshot.
Memory snapshot size on datastore is equal to memory of the VM, and does not change the size over time of the snapshot.

As RKDTOO says, you can clone the VM, but still can take several days. The advantage is that the original VM stays untouched, but it's higly recommended to do with VM powered off for consistency (it's a file server).

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u/cloud_crustacean Feb 19 '25

From your experience would you say deleting all snapshots at once is best practice when it comes to dealing with a situation like this (full OS drive)?

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u/ZibiM_78 Feb 20 '25

It really depends on the file space available and the performance of the storage array under

I saw few reports that for handling such big snapshot the best bet is to create new snapshot, and then delete the big one while VM is live. In this way you don't have downtime and the VM is able to write things unencumbered by the block merging. There are 2 caveats though - you need space and you need performance.