Louwrentius

Currently, I am running VMware ESXi 4.1 on a test system. To manage ESXi, you need the VSphere client, which is only available for the Windows platform. Therefore, I run VMware Fusion on my Mac to be able to access VSphere and manage my ESXi host.

The trouble is that both ESXi and VMware Fusion use the control-alt shortcut to release a console. So as soon as you start using a console within the VSphere client which itself runs within VMware Fusion, you cannot get back to the Windows OS.

You will have either access to Mac OS X or the ESXi guest. And to top it of, the mouse just completely disappears on Windows.

To get arount this problem, you need to somehow be able to send a control-alt sequence to the Windows guest withouth actually pressing control-alt.

Fortunately, VMware fusion allows you to create a key mapping that allows this.

Within the preferance pane, the first tab is called Key Mappings. You can create a new key mapping. For example, I mapped control+q to control-alt. This allows me to get out of the ESXi guest within the VSphere client, witouth getting grown back to Mac OS X. As a side effect, the mouse also showed up again, which is to be expected.

I'd like to introduce the utility 'dstat'. Dstat provides detailed statistics about what is currently happening on your Linux box.

Dstat allows you to monitor the system load, disk troughput, disk io, network bandwith, and many more items.

Dstat is so valuable because it provides you with all required information on a single row that updates every so often. It is a great tool for debugging system performance. An example of the output of dstat:

Click on this image to view the dstat output at the original size. It will tell you a small story on what happened on the system.

As you can see, a copy action is going on between two disks. Then suddenly, some other process is writing data to the source disk. Both read and write performance drops. As soon as the additional writing process stops, the read and write performance of the still running copy process returns back to normal.

The real benefit of this utility is that it clearly provides almost all information you might want to know in a single line.

One of the most used options are the disk throughput and network throughput columns. By default, dstat displays the aggregated throughput for all disks and network cards. You can bypass this behavior by specifying individual disks or network devices with the -D or -N option, like:

dstat -D sda,sdb -N eth0,eth1 20

Please note that the '20' argument at the end specifies how often the screen gets updated. Thus every single row is the average of that 20 second time frame.

For a full overview of all options that are available, issue the 'dstat --list' command.

You may find it very useful.