Server Fault is a question and answer site for system and network administrators. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

DISCLAIMER: I'm a programmer, not an admin!

I am setting up web apps in a new server cluster and copying files using xcopy or robocopy and UNC paths between servers on the same subnet is really slow. SOmetimes it seems to sporadically speed up, other times it is taking 2+ seconds to copy 5K files. On our old environment this was lightning fast. The only difference I know of is that was Win2K3 and this is Win2K8. Could OS have anything to do with it, or is this more likely a weird network issue causing this?

share|improve this question
What robocopy options are you using? – joeqwerty Feb 24 '10 at 23:28
Pretty much any options, but usually just /S - it's the actual copying that takes a while. The weird thing is sometimes I'll run it (same options) and it copies with the speed I'd expect other times I can sit and watch the percentage complete slowly change for small text files, etc, that should be so fast I don't even see the progress changing. – Brian Donahue Mar 1 '10 at 14:16

Try adding /MT and removing /Z. This worked like a charmm for me:)

share|improve this answer
This change took my network utilization from 5% to 50% for a million file copy of 500kb files. – Keith Sirmons Mar 23 '15 at 16:59

Have you considered the possibility that your new server cluster has a different virus-killer, which might be set up incorrectly.

Just a thought, but this can slow filetransfers sometimes.

share|improve this answer

Double check you don't have TCP Offload enabled as well. That can impact file copy speeds.

share|improve this answer

Is it slow in both directions? Is it slow from all other machines to the new box(s)?

Make sure there isn't a speed/duplex mismatch between a NIC and switch, disable auto-detect if it's on.

share|improve this answer
So far it seems to be slow in all directions. I'm going to share these comments with my network admin and see if he can find anything. Thanks! – Brian Donahue Mar 1 '10 at 14:16

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.