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We have recently upgraded our network to Windows 7 clients with Windows server 2008 servers. The upgrade was completed by the end of September and until now has been fine (apart from the minor bugs).

Recently (within the last 2 weeks) we've notice all computers on the network (around 1000) start to slow down to the point their unusable. It starts at about 08:45 and finishes at 09:15. Because of this, we think something may be broadcasting across the network.

This happens every day, between these times. I cant use my computer at all at the slowdown peak, and looking at task managers performance graphs, Physical memory is hovering around 35% and CPU usage is at 0-10% (idle) yet still crashing.

I've looked on DHCPs server log and cant see anything which stands out.

The only change we made prior to the slowdown was installing adobe CS6 on some computers, however the slowdown affects computers without CS6.

We have 2 physical machines, each with around 5-7 virtual machines running on them with ample memory.

Does anyone have any suggestions as to what we can do to narrow down whats causing the crashes? Any help, suggestions or advice would be appreciated.

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My first thought is Anti Virus –  Dan Nov 12 '12 at 10:04
    
My second thought is Microsoft Outlook. –  Tom O'Connor Nov 12 '12 at 10:24
    
@Dan we thought that as well, however AV is scheduled for 5pm (after everyones left). –  Phil Cross Nov 12 '12 at 11:49
    
@TomO'Connor Unfortunately we've migrated over to Office365 rather than hosting our own exchange machine (which I prefered!) –  Phil Cross Nov 12 '12 at 11:50
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@inhabitant I deleted all scheduled tasks on my computer and it still happened. Nothing in the logs which stood out. We found out it was System Center Config Manager trying to remove software on all computers which was already removed. Thanks for your response :) –  Phil Cross Nov 13 '12 at 15:09
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2 Answers

Is there is a dump file made (MEMORY.dmp) in system32? You can analyze that dump file with the Debugging Tools for Windows, in most the crashes the dump file shows the driver which is causing the crash.

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Thanks for the advice, I'm going to try check it now. I'll reply if I find anything. –  Phil Cross Nov 23 '12 at 9:10
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I am not a "Windows guy" but, could you use something like wireshark and check out the network traffic on a few boxes and see what is happening on the network? I guess that would be my response for Linux boxes....pull out wireshark and see what is going on at that time. Sorry, if that is stupid or you may have already done so!

Is there a common disk between these boxes...is there some big old SAN that could be getting busy...like somebody backing up a database to the SAN...and slowing down everybody?

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We do have a large brand shiney new SAN, however If it was that getting clogged up, I would have thought the slowdown / crashing would appear during the day, everyday rather than within a half hour period primarily on a Friday :( Thanks for your help though :) –  Phil Cross Nov 23 '12 at 9:11
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