Josef "Jeff" Sipek <>

If you would like to contact me about any of my code/ideas/etc., you have two main choices...
Then there is always my blahg and mastodon.


I am an engineer at Nutanix working on the Acropolis Hypervisor.

Previously, I was an engineer at VMware working on the virtual machine monitor (2021-2024), Open-Xchange working on Dovecot (2016-2021), Nexenta Systems (2014-2016), and at Barracuda Networks (2011-2014).

Prior to joining the industry, I was a PhD student in Computer Science and Engineering at the University of Michigan (until April 2011, M.S. only), and a B.S. student in Computer Science at Stony Brook University (until December 2007).

While at the University of Michigan, I worked with Peter Honeyman on I/O performance of systems and with Jason Flinn on distributed filesystem metadata caching on flash-based solid state drives. And while at Stony Brook in the File system and Storage Lab (under the guidance of Prof. Erez Zadok), I worked on Unionfs (a stackable namespace unification filesystem) and FiST: Stackable File System Language and Templates.


My programming languages of choice are C (but not C++) and shell scripting. I'm a fan of Mercurial for source code management.

Current projects

I don't always work on each of these, so their development is quite bursty. After all, these are all hobby projects.

Past projects

The following few projects are either obsolete (due to the underlying tools not being available), or just not actively maintained due to lack of time or interest. Let me know if you want to take over the maintenance of any of them.
For completeness sake, here is a list of partially developed projects (work-in-progress) that I've abandoned but which may be of interest to some people.



Publications & Workshops