Storage improvements from Windows Server 2008 SP1 Hyper-V to Windows Server 2008 R2 Hyper-V

 

The following table shows changes in storage.  Some of the changes are performance related like hot add of storage.  This helps performance by reducing the time it takes to add new storage.  The big things to note are increases in IO Sizes passed from VM’s and huge improvements in Dynamic VHDs.

 

Virtualization Feature	WS08 + RTM Hyper-V	WS08 SP2 Hyper-V	Windows Server 2008 R2 Hyper-V
Dynamic VHD Performance	Writes 3x slower than fixed. This is due to limited meta data caching.	Writes 3x slower than fixed. This is due to limited meta data caching.	Dynamic and Fixed Disk performance at almost parity
Diff Disk Scaling Performance	1x	1x	4x – 5x
IO Sizes (Virtual SCSI)	64KB	64KB	8MBytes (improves throughput)
IO Size (Virtual IDE – no changes just for comparison)	64KB	64KB	64KB
VHD Block Size	512KB	512KB	2MB
Fixed VHD Creation Speed	1x	1x	3x – 4x
Hot add of storage	No	No	Yes
SCSI Command Pass-through	No	No	Yes

 

** Fixed Disk is highly recommended for Production