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smoseley
Contributor
Contributor
‎02-18-2009 09:03 AM

VMWare copy slow to SAN

We have a couple of VMWare hosts connected via fiber to a XioTech 3D SAN that we're using for our VMotion cluster. Our Virtual Servers seem to work fine and so does vmotion, but when we try to copy large files to the SAN using Datastore Browser or Veeam FastSCP, we get transfer rates of about 5MB/s whereas when we perform copies between host local disks or even from a host local disk to the same XioTech 3D on a different LUN attached to a Windows 2003 Server we get 50 or more MB/s.

Does VMWare do something different with SAN data transfers that could cause the speed issue we're seeing?

Thanks.

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4 Replies
askewview
Contributor
Contributor
‎02-20-2009 11:08 AM

It could be that those utilities are doing a single threaded copy where as the other copy mechanisms are multi-threaded.

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Rob2E
Contributor
Contributor
‎02-25-2009 01:14 PM

I too am getting approx. 5MB/s with Datastore Browser.

I have been told that the "admin" functions are restricted in how much resources they can take, so that they do not impact on theVM performance.

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smoseley
Contributor
Contributor
‎02-25-2009 01:24 PM

Thanks, but if that were true, wouldn't it restrict the resources whether you were accessing local disk or the SAN? In our case, it only affects SAN writes.

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Rob2E
Contributor
Contributor
‎02-26-2009 07:04 AM

Neat.

Never tried to do anything before today with my local hard drive. It's been just a place for the VMware OS.

In Maintenance mode, I can copy from the SAN (iSCSI) to the local hard drive at 20MB/s, using copy and paste in DataStore browser. This means stopping all the VMs.

Rob

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