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I am trying to run some P2V conversions using SCVMM 2012 Release Candidate. The source machines are Windows Server 2008 SP2 hosts in a local network. The destination is a Hyper-V 2008 R2 SP1. Unfortunately, the conversion is rather slow - I get around 3-6 MB/s for the data transfer. I suspect BITS for slowing things down, but have not figured out the definite root cause yet.

Edit: The type of conversion seems not to matter much - I see similar results for offline and online conversions. After starting four parallel conversions the Hyper-V performance graph for disk write throughput (MB/s, red line) against idle time (percentage, blue line) looks like this:

perfmon graph

The spikes in the write throughput graph tell me that something is pausing the data transfer every other second. Also, since it would just look too artificial to have four source machines pause sending synchronously, I suspect the Hyper-V or SCVMM side of things to cause the slowdown.

Any ideas on how to speed things up?

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up vote 1 down vote accepted

I've done a few P2Vs using SCVMM. I'd have to go back at the logs and look but I recall my experiences being fairly slow as well when doing multiple conversions, but yours seems absurdly slow.

A few things came to mind when reading your question:

I wonder if you are bogging down the destination drives and are waiting for the controller to flush the cache to disk? What does it look like when doing a single VM at a time? (Does the traffic seem more consistent or does it follow the same pattern). Does the data have a good stable path from the Physical box to the SCVMM box to the Hyper-V box? (thinking maybe one of the links is slow or saturated and you are fighting other "network" traffic). Is the physical box capable of going faster than the speeds you are experiencing? (I'll assume yes, but I felt compelled to ask). Have you tried P2V to a different Hyper-V box?

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Mike, thank you for your answer. I've noticed a recently added bottleneck in the routing configurations - the routing path between the converted machine and the Hyper-V host has changed recently and was going through a 100 Mbps interface. I've changed this to get a Gigabit routing path throughout and the transfer rates increased to 12-15 MB/s (still poor, but better). I think BITS is doing some "idle data rate" calculations and limits the transfer bandwidth based on that. I was unable to find any parameters to tweak this, though. –  the-wabbit Mar 1 '12 at 13:42
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