Wednesday, April 17, 2013

The Dangers of "Perpetually Pausing" VMs using VMWare Workstation

As a long-time user of VMWare Workstation, I am particularly fond of "pausing" my virtual machines and leaving them in a suspended state.

The major benefit of doing this, for me, is that the next time I resume my virtual machine, I can simply start up my virtual machine and pretty much resume working where I left off earlier.  This is because VMWare Workstation saves the "entire" state of the virtual machine for me.  This means that every application that I left open including browser windows, instances of Visual Studio, SQL Server Management Studio and any other miscellaneous apps will be in the exact same state as when I left it.

However, there is one big "danger" of perpetually pausing a virtual machine rather than occasionally shutting it down and re-starting it.

As I stated above, each time we pause a virtual machine, VMWare saves the entire state of the machine.  Assuming that you never fully shut down the virtual machine, the state of the machine will continue to grow and grow over time.  In addition, the memory consumption within the virtual machine (assuming is it some flavor of MS Windows) will eventually begin to grow as well.  Therefore, over time, the resources of this virtual machine will become heavily depleted and the time and resources required to resume the former state of this virtual machine will place a heavy load on the host machine.

For example, if you pause a virtual machine a handful of times, VMWare Workstation may only take a few seconds or a minute to resume the virtual machine.  However, if you end up pausing the virtual machine dozens upon dozens of times, eventually you will encounter a "freeze" or "deadlock" condition when attempting to resume the virtual machine.  On my Windows 8 Enterprise Laptop which has an Intel i7 Processor and 32 GB of RAM, resuming one such virtual machine on my system FROZE all applications from operating on my machine for nearly 10 minutes!!

Therefore, take my advice and periodically shut down and restart your virtual machines rather than constantly pausing them.  It will save you some time, energy and plenty of frustration....

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