Simple statistics for performance analysts.

As performance analysts we often have to summarize large amounts of data in order to make engineering decisions or understand existing behavior.  This paper will help you do exactly that!  Many analysts know that using statistics can help, but statistical analysis is a huge field in itself and has its own complexity.  The article below distills the essential techniques that can help you with typical performance analysis tasks.

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Statistics for the performance analyst

Work around for bios.hddOrder when creating an OVF/OVA template.

When changing SCSI devices in an ESX based VM, it’s easy to screw up the ability to boot.  The simple fix is to add

bios.hddOrder = “scsi0:0”

to the end of the .vmx file.  This has always worked for me.  The problem with this solution is that any OVF/OVA that is created from the VM will not include the .vmx file hack, and of course VM’s created from the template will not boot until their .vmx file is hand edited.

The solution that worked for me was to simply make the “boot drive” the first .vmdk file that is listed in the .vmx file.  In my case, the Linux OS is stored on the VMDK named “disk.vmdk”

In the before case, this disk is listed last (even though it has SCSI ID 0:0:0) and the VM does not boot.

I simply change the filename from disk_6.vmdk to disk.vmdk (and change the last item from disk.vmdk to disk_6.vmdk).

The beauty of this method is that the ordering is maintained when creating an OVF/OVA.

When the VM boots, the /dev/sd devices may change since the vmdk’s are now attached to different SCSI devices – so mounting using UUID’s in Linux helps keep things sane.

Before

After

Note: I tried editing the .ovf file and adding a key:value pair to the file, and regenerating the SHA1 and stashing the SHA1 in the .mf file.  The process worked, but the VM still did not boot, and the bios.hddOrder param was not in the .vmx file of the VM that was created from the template.