An important benefit of vSphere Virtual Volumes (vVols) is in its handling of snapshots. With VMFS-based storage, ESXi takes VM snapshots by creating a delta VMDK file for each of the VM’s virtual disks. It redirects new virtual disk writes to the delta VMDKs, and directs reads of unmodified blocks to the originals, and reads of modified blocks to the delta VMDKs. The technique works, but it introduces I/O latency that can profoundly affect application performance. Additional snapshots intensify the latency increase.
The performance impact is so pronounced that both VMware and storage vendors recommend the briefest possible snapshot retention periods - see Best practices for using snapshots in the vSphere environment (1025279) kb article. Practically speaking, this limits snapshot uses to:
Patches and upgrades
Taking a snapshot prior to patching or upgrading an application or guest operating system, and deleting it immediately after the update succeeds.
Backup
Quiescing a VM and taking a snapshot prior to a VADP-based VM backup. Again, the recommended practice is deleting the snapshot immediately after the backup completes.
These snapshots are typically of limited utility for other purposes, such as development testing. Adapting them for such purposes usually entails custom scripting and/or lengthy copy operations with heavy impact on production performance. In summary, conventional VMware snapshots solve some problems, but with significant limitations.
Array-based snapshots are generally preferable, particularly for their lower performance impact. FlashArray snapshots are created instantaneously, have negligible performance impact, and initially occupy no space. They can be scheduled or taken on demand, and replicated to remote arrays. Scripts and orchestration tools can use them to quickly bring up or refresh development testing environments.
Because FlashArray snapshots have negligible performance impact, they can be retained for longer periods. In addition, they can be copied to create new volumes for development testing and analytics, either by other VMs or by physical servers.
FlashArray administrators can take snapshots of VMFS volumes directly, however there are limitations:
No integration with ESXi or vCenter
Plugins can enable VMFS snapshot creation and management from the Web Client, but vCenter and ESXi have no awareness of or capability for managing them.
Coarse granularity
Array-based snapshots of VMFS volumes capture the entire VMFS. They may include hundreds or thousands of VMs and their VMDKs. Restoring individual VMDKs requires extensive scripting.
vVols eliminate both limitations. VMware does not create vVol snapshots itself; vSphere directs the array to create a snapshot for each of a VM’s data vVols. VASA then translates vSphere commands into FlashArray operations. VMware administrators use the same tools to create, restore, and delete VMFS and vVol snapshots, but with vVols, they can operate on individual VMDKs.
With Purity//FA when taking a managed snapshot the array will copy the VMs current data volume/s to new data volume/s that has a 'snap' suffix for it. Keep this in mind from an object count perspective. Then when creating a managed snapshot there will be an additional array volume created for each virtual disk.