Disk Snapshot Implementation about bosh-vsphere-cpi-release HOT 3 CLOSED

Hey @allomov! I'm not super familiar with vSphere snapshots so please correct me if something looks off. My understanding was that a vSphere "snapshot" is used to store the state of a VM (e.g. memory contents) to allow you to reset the entire machine to a previous state. The BOSH concept of a snapshot is about storing a "backup" of a single disk. The vSphere snapshots deal with persistent data in a weird way, where by default the data is written to a redo log until you take a snapshot, at which point the data is actually written to the underlying disk. More info here. We disable this redo log in the CPI so all writes go to the underlying disk immediately, so your persistent disks are not covered at all by vSphere snapshots.

Given all that, is there a vSphere-native way to take a disk snapshot? Copying the underlying .vmdk file seems the closest that comes to mind, but that feels a bit strange. Did you have something in mind?

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Actually I only have a request to create snapshots for VMs created by BOSH. I'll discuss this issue with vShpere operators and will return to it later. Thank you for the answer.

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@allomov feel free to reopen if necessary.

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