• Slow network performance for Windows Server 2008 guest on vmware ESXi 4.1

    28Jul
    Author: trent Categories: Infrastructure Comments: 4
    tcp lego header

    TCP header, Lego (tm) style

    The older I get, the more lessons I seem to learn (or, not learn) over and over.  Have you ever seen TCP offload work correctly?  Of course not!  I’ve been bitten by a TCP offload (aka TCP Offload Engine or TOE) problem in just about every environment I’ve touched in the last 20 years, and sadly this week was no exception.

    To make a long story short, we have a production vmware ESXi 4.1 host with both Linux (CentOS) and Windows Server 2008 guests.  No problems were reported (or measured) with the Linux guests, but the Win 2008 guests suffered from extremely choppy network connections, for common services like Remote Desktop and backups (including lost connections).  As you probably know, I’m big into actually investigating the underlying cause of a problem rather than randomly throwing darts at it, and as such I grabbed some packet traces with wireshark.  Check this out:

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  • Exploring your NIC for fun and profit

    12Jan
    Author: ben Categories: Infrastructure Comments: 0

    Pile o' NICs

    I know, you love your network card. You installed Linux, the NIC was autodetected at first boot, and everything “Just Worked.” Your server has been happily providing services over the network ever since.

    But what do you really know about your network card? Is it the culprit of slower performance for your CPU-intensive application? Could you benefit from any of its advanced capabilities? Today’s network interface cards offer a number of hidden gems to the savvy administrator. In this article we’ll learn some of the most important tricks to understanding your NIC in Linux. Read more »

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