In Virtual SAN 6.0, a new snapshot format was introduced called vsanSparse. This improves snapshot functionality by leveraging the new VirstoFS on-disk format used with VSAN 6.0. I had a question recently about what would happen if I migrated a VM with a traditional vmfsSparse/redo log type snapshot. The question was whether or not it would be converted to the new vsanSparse format. Similarly, what if a VM with a vsanSparse snapshot was migrated from VSAN to a traditional VMFS/NFS datastore? Would it also be converted between formats? I decided that the only way was to try it out.
There is a new snapshot format introduced in VSAN 6.0 called vsanSparse. These replace the traditional vmfsSparse format (redo logs). The vmfsSparse format was used when snapshots of VMs were taken in VSAN 5.5, and are also the format used when a snapshot is taken of a VM residing on traditional VMFS and NFS. The older vmfsSparse format left a lot to be desired when it came to performance and scalability. This KB article from our support team, indicating that no snapshot should be used for more than 72 hours, and snapshot chains should contain no more than 2-3 snapshots,…
Well, I got so many questions about my previous articles on a new way of doing snapshots with VVols that I decided to take the time and get even deeper into their behaviour. In this setup, I take a Windows 2008 Guest OS running in a virtual machine deployed on an NFS datastore, and I compare it to an identical VM deployed on a VVol datastore. This is purely from looking at how we do snapshots. Remember with VVols, snapshots always run on the base disk, compared to the traditional way of doing snapshots where the VM always run on the…
This is possibly the most exciting new storage feature in the vSphere 5.1 release. Space Efficient Sparse Virtual Disks (or SE Sparse Disks for short) were designed to alleviate two issues. Let’s describe these issues first of all. Problem Statement #1 – Let’s take a Guest OS running on a linked clone (View desktop if you will), and this Guest OS issues a 4KB write. vmfsSparse disk (which is the format used by traditional linked clones) has a block allocation unit size of 512 bytes. In other words, this Guest OS is backed by 512 byte blocks. Depending on the…