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Record Replay, the technology that allows you to reproduce what’s going on in a virtual machine with machine-level instructions, has been shown off at VMworlds past, but is just now coming into its own. You could experiment with it a bit in Workstation 6.0, but it is now available in a useful way in VMware Workstation 6.5, (in beta but has a new Release Candidate). Let’s let E Lewis introduce it in his new blog. Link: Better Software Development with Replay Debugging: VMware Workstation 6.5: Reverse and Replay Debugging is Here!.

I’m
proud to announce that VMware Workstation 6.5 includes new experimental
features that provide replay debugging for C/C++ developers using
Microsoft Visual Studio. Replay debugging allows developers to debug
recordings of programs running in virtual machines, and it is valuable
for finding, diagnosing, and fixing bugs that are not easily
reproduced, a particularly challenging class of bugs. Once the
manifestation of a bug has been recorded, it can be replayed (and
debugged) over and over again, and it is guaranteed to have
instruction-by-instruction identical behavior each time. In addition,
Workstation includes a feature that simulates reverse execution of the
program, making it easier to pin point the origin of a bug.

Aside from being insanely cool and perhaps the end of the heisenbug, I think this shows how VMware’s 10 years of experience manifests itself in innovation. Virtualization is about more than server consolidation, and once you are virtualized, the really interesting things can start to happen.

Here’s E demonstrating how this works. I think the UI has changed a bit since we filmed this. We’re running Visual Studio on the host, outside the VM, and attaching to a process inside the VM and putting in triggers and whatnot in the debugger as it replays until we track down the bug we’re looking for. If we go too far, we can always hit rewind.

Oh, and there’s a Lenovo laptop to be won: VMware Record and Replay Challenge