Transfer speed difference with pass-through hyper-v disk?

[rpeters83]

I have a SATA drive in my hyper-V host. Previously, I was exposing it as a share directly from the hyper-v host. My read transfer speeds were about 110MB/s.

I since then have fed that drive through a windows 2003 r2 server instance and made a share of this same drive through that as a pass-through disk. My read transfer speed then dropped to about 85-90MB/s. All speeds were tested several times and are consistent.

Why the drop? I can't tell if it's 2003 R2 server that is holding me back or the fact that it's now routed through a VM guest. I thought pass-throughs were nearly identical performance.

Thanks.

 

[arcusfront]

You did not specify which version of Hyper-V you are using. With Hyper-V 2012. there is very little to gain (and some to loose) by using pass through disks. The new .vhdx disk format will provide reliable performance then a pass through disk...regardless of OS. On our test server (Dell T420 w/ 2x Quad Core processors,) copying and restoring, running queries on upwards of 10 GB sized SQL databases, there are no perceptible performance issues while using .vhdx disks.

As for Server 2003, it is a real dinosaur in terms of technology and any modern server version such as 2008 or 2012 will outperform in all areas such as disk I/O management, memory management etc.