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File Copies Slow On Hyper-V Guest

Posted on 2014-02-06
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Last Modified: 2014-11-12
Hi Experts!

I'm concerned about some file copy speeds I'm experiencing and am hesitant to push our New Server up to production.

He is the Basic setup and what I am Experiencing.

My question to start with I suppose is - 'Is this behavior Normal?"


Here is the basic setup;


We have a New server (Windows Server 2012) running only the Hyper-V Role.

This runs 2 Hyper-V Guests both are Windows 2008 R2.

1 is going to be a DC only. The 2nd is setup with the File Server role Only.

ALL below copies take place on the same Physical Hard Drive;


Concern 1;


Remotely Logged on to Hyper-V Host - Copying a large 5gig file from D:\VHDX\Start directory to D:\VHDX\Finish Directory is unbelievably quick - Speeds average out around 500MB per second after an initial Burst over 700MB!

Remotely Logged on to Hyper-V Guest - Copying same large 5gig file from D:\Start directory to D:\Finish Directory is quick  - but nowhere near as quick as the above - Speeds average out around 130MB per second after an initial Burst of around 190MB

Whilst this seems pretty good - I'd love to be able to take advantage of the FULL Speed.

Is this normal? Am I really losing this amount of capacity by going Virtual!?



Concern 2;

Copying the same files but across VM's (whilst remotely logged onto either Host or Guest) goes at Gigabit Speed, so all fine there!?  ... but ...

Doing exactly the Same Copies (so Host to Host and Guest to Guest on Same D Drive) from a Windows 7 PC (All gigabit)  Goes around 40-50MB

Again is this Normal? or am I losing some performance?


Hope you can help. Ive tried a multitude of  VMQueues, Offloads, AV Disabled, Firewalls Off etc. but don't seem to be able to get anywhere near the same performance from the Guest as the Host and am therefore struggling to see the benefits of Visualization  for our AD and Files Server requirements.


Thanks in anticipation.

Paul
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Question by:PaulStar
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Expert Comment

by:Eric B
ID: 39839753
You are copying files via the network and not local disk when going from host to host. If you create a private network between both hosts, that may help.
Consider that hyper-v virtual adapter may need some tweaking like tcp chimney mode, etc.
You are also copying via network share I assume?
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Author Comment

by:PaulStar
ID: 39841508
Hi Eric,

In "Concern 1"  -  I don't see how I'm copying across the Network?

Perhaps your answer is therefore only in relation to "Concern 2"; In which I am copying via the Network. I have tried every offload available within Physical Nic, Virtual Nics and the Virtual Switch - all to no avail.

I assume from your response that this is not normal behavior and that I should be seeing better performance from the Hyper-V Guest in both of my concerns?
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Expert Comment

by:Eric B
ID: 39841781
I think it is "normal" behaviour because of copying via shares/smb etc...I think it is worth looking at setting up iScSi server on the host and then connecting the drives using iScSi target/MPIO connectivity.
This is usually when connecting to a san drive or when you use sql or hyper-v clustering.
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Author Comment

by:PaulStar
ID: 39842527
Thanks Eric

This is new territory for me ...

"I think it is worth looking at setting up iScSi server on the host and then connecting the drives using iScSi target/MPIO connectivity."

.. but I'll look into it and see if I can get a test going!


In the meantime any other input, advice or thoughts would be appreciated!
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Expert Comment

by:Eric B
ID: 39842826
Its also much faster because MPIO, if using multiple NICS, will connect to the drive using multiple paths.
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Author Comment

by:PaulStar
ID: 39847229
Thank agin for your input! ... I setup the iScSi server on the host (windows 2012) and connected the Guest (Windows 2008 R2) but seem to have lost some more more performance.

From the two starting benchmarks;

Original Host To (same) Host;
Remotely Logged on to Hyper-V Host - Copying a large 5gig file from D:\VHDX\Start directory to D:\VHDX\Finish Directory is unbelievably quick - Speeds average out around 500MB per second after an initial Burst over 700MB!

Original Guest to (same) Guest
Remotely Logged on to Hyper-V Guest - Copying same large 5gig file from D:\Start directory to D:\Finish Directory is quick  - but nowhere near as quick as the above - Speeds average out around 130MB per second after an initial Burst of around 190MB

I now get;

NEW iScSi Guest to (same) Guest
Remotely Logged on to Hyper-V Guest - Copying same large 5gig file from E\Iscsi:\Start directory to E\Iscsi:\Finish Directory - Speeds average out around 75MB per second after an initial Burst of around 110MB.

I have not configure MPIO as I do not have spare NIC Capacity. But in all honesty the Network is not production, has no other traffic on it and isn't being  pushed in any way.

Also I am still unclear why this would be using the network at all - Apologies if that is a stupid statement but this just seems like a straight forward file copy on the same disk, albeit being remotely logged on to action it?
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Accepted Solution

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Eric B earned 500 total points
ID: 39847435
An other thing I had noticed with network file copying is the block size used for transferring files.
If you use a disk performance tool like HDTune (http://www.hdtune.com/)
and you "play around with the file block transfer size, you may see some very surprising results!
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Author Comment

by:PaulStar
ID: 39995773
Didn't get to the bottom of this and had to move on. Wasted way too much time on it. Happy to give Eric the points for his help ... I did learn a few things along the way - Thanks Eric!

Will update if ever resolved.
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