Written by James McDonald

July 1, 2012

For much of the last 10yrs I’ve had a flirtation with virtualization. I bought a VMWare Workstation License and played and fiddled with Virtual Machines, usually for training and testing purposes. My parrallel love of all things Open Source has meant virtualization technology has been a constant companion to check out each flavour of Linux that blooms and whithers out on the Internets.

When VMWare made it’s VMWare Server and ESXi products free I installed then at work and ran the “Server” product on my workstation for testing and dev and ESXi on a Dell server to run 3 or 4 guests in place of purchasing more and more physical servers. But with the ESXi product there was no redundancy. If I lost that one ESXi host I would be stuck.

So I went with two Dell R710 Servers backing onto a EqualLogic iSCSI SAN running VMWare Essentials Plus Bundle. The servers have 64GB RAM each and my EqualLogic array is half filled with 12 disks in RAID 10 configuration with two hot spares. It’s interesting to note that they said I could handle all my processing load on a 1GB SAN Fabric but knowing I was heading towards an SQL Server installation meant I upscaled everything to allow for that.

I ended up paying Dell to give me an implementation consultant for a few days. The guy had masses of VMWare experience (he came from a 600+ VM environment) but more importantly he was also a CCNP so before we got bogged down in VMWare he helped reconfigure my network.

The network intersubnet communication was being choked down to 100Mbps by a ‘router on a stick’ configuration hanging off an ASA firewall. The problem was that I had a layer 3 gigabit switch further in that would forward packets at closer to 1Gbps. But with the router-on-a-stick ASA routing config my backups from other subnets were taking a long time and the VMWare environment running hosts from all different subnets would have been hobbled back to 100Mbps when they attempted inter-subnet communication. So a few Cisco commands later the Cisco Layer 3 switch was doing the subnet routing and the ASA was doing what it should have always done which is firewalling only.

A few things struck me with a VMWare implementation:

You don’t want to do it totally on your own if you are inexperienced. There are just so many tweaks and performance gains to be had by getting a trained pro in. For example I got a 10GB SAN fabric. But unless you are aware that you should be running Jumbo Ethernet Frames of 9KB instead of 1500 Bytes you could be hamstringing your Storage Area Access speeds.

There are a whole lot of other things that might not be apparent to a standard small company system admin. Sometimes it’s advantageous to bring big company experience into the theatre of a small company to get a more robust configuration.  

I did find that VMWare no longer is hot for cold cloning (unless you have an enterprise VMWare license). I couldn’t find the coldclone.iso image they talked about and I wasn’t keen to spend hours hacking together a Windows PE boot image that includes the VMWare Convertor software. So to get a Windows host that is running disk-busy applications cleanly Physical’d to Virtual’d (P2V) you need to disable as many disk writing services as possible while you do the P2V. I discovered running msconfig and disabling services temporarily will give a good result when  you do the P2V process. Once the converted machine is on the VMWare host you can boot and re-enable the services and you have a solid running VM.

It’s a suprisingly unexciting process. Just remember to physically unplug your network adaptors on the Physical machine so you don’t accidentally boot and create a clash on your network.

Once your operating systems are running on VMWare you inherit so much more flexibility. Disk space running out on C:? Just change the harddisk size in VMWare and boot into your VM and then right click on the disk in storage management and extend the volume. Amazingly simple. Need to do some destructive testing with an OS installation? Right click and clone the VM and you have your sandbox ready for fiddling.

Downsides …. eggs in a basket… stability in a vmware environment relies on the SAN and the servers being stable. If you have to shutdown the SAN for maintenance (which I had to do) you (temporarily) lose all your hosted services.


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