Russian doll storage: Performance impact?

[OIMJB]

Hi,

What is the performance impact of "storage in a storage in a storage", aka multilayered storage for VM.
Ex:
Scheme 1: PHY-STARWIND-VHD
Layer 0: Physical disk (and logical drive)
Layer 1: Starwind image file (.img) (and logical drive associated with when connected)
Layer 2: VHD (and logical drive)

Seems to be a lot of layer before guest OS deal with physical drive.

And Scheme 2: Passtrhought storage
Layer 0: Physical disk (and logical drive)
Layer 1: Starwind image file (.img)
And passthrought(ed) to VM directly.

Between these 2 possibilities, a better performance is expected for less layer?

[anton (staff)]

1) FLAT (Image file) layer is very thin. We do use file system services to reserve space for file only. All I/O is direct and caching is also our own.

2) LSFS does *accelerate* I/O (of the particular workload) so think about it as of a turbocharger in your car.

3) Pass-thru should be generally avoided with hypervisors. Lots of reasons (live movement of a VMs, snapshots, FT etc).