Mounting your VOB 101: Slow down there, partner!

The purpose of this post is to help others who find absolutely no useful information if confronted with the following message while mounting a ClearCase VOB:

Mounting MVFS filesystem \<VOB>.
cleartool: Error: Unable to mount: File exists

I found this odd error message in my Build Forge logs this morning. I have several automated jobs that rely on scripts being pulled from ClearCase VOBs. When the Build Forge job went to mount the VOB, this was the error it encountered.

Now, keep in mind, this type of Build Forge job has been running for over a year. This particular job has been running for at least a week now. I’ve never seen this error before.

I Googled the error “Unable to mount: File exists” and what did I find? Nothing. Absolutely nothing. Never a good moment in the life of a ClearCase administrator! So what’s the next step? Well, I figured checking the MVFS logs might help since mounting a VOB is an MVFS action. Voilá! A message I hadn’t ever seen before here either.

[<timestamp>] mvfs: Ok: INFO: {<pid>/<tid>}
IoCreateSymlink failed: MVFS drive symlink already exists.

(That was all on one line…I just broke it up for formatting purposes.) This looked promising. Surely someone else has encountered this odd message before.

Awesome…6 results! Not so awesome: none of them refer to mounting a VOB in general. They are all about ClearCase and Distributed File System (DFS) support (or, rather, non-support). That doesn’t really help me out.

With no one else out there seeming to have had the same problem, I started asking myself what might cause this problem. Well, it just so happens that this Build Forge job is one of two new jobs I introduced last week. I already had two other jobs running on a similar schedule. All four jobs end up running at exactly the same time this one job failed. All four jobs end up trying to mount the same VOB on the same machine (they all run on the same server). Is it possible that ClearCase ends up croaking because of 4 nearly-simultaneous attempts to mount the same VOB? Is it more generalized and it’s the attempt to simultaneously mount anything that’s causing the error? Unless someone else is willing to devote some time and try to find out, I’ll quote the Tootsie Pops commercial narrator: “The world may never know.”

The job is running fine now. I expect it was a “perfect storm” scenario and we might run into it every week or so. Am I happy with that? No. Will I live with it? Yes. And maybe you can too if you found this page looking for help to this mysterious set of error messages.


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2 Responses to Mounting your VOB 101: Slow down there, partner!

  1. Jamie says:

    Hi there Archimedes,
    You might be happy to know I too have had a similar issue relating to (IoCreateSymlink failed: MVFS drive symlink already exists)

    A ClearCase user contacted me today because he couldn’t check out a Word doc, kept getting a “Access Denied. Contact Your Administrator” error dialog. Sooooo, I went a lookin’ on the Web and viola! a link to your blog.

    I found this bit of nastiness (IoCreateSymlink failed: MVFS drive symlink already exists) in the mvfs.log file on my ClearCase server, but since we’re not running DFS and none of the DNS names have changed I’m frankly quite puzzled. Ended up rebooting the server and the ‘Access Denied’ messages went away. Small shop here, so simultaneous mounting of vobs maybe out of the question, but it was good to find someone else at least makes reference to the issue.

    – Best

    • Jamie, that’s really interesting. Obviously there’s something more to this error message than I originally thought. I’m glad that I was able to help you feel a little less lonely when searching for another instance of this odd message that didn’t involve DFS.


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