Not sure what happened here, and I've searched the internets to no avail, so I thought I'd ask.

I think a week or so ago, I had a system crash, and after rebooting, I relaunched FCPX from a "version save". Since then I've noticed FCPX slowing down and also that it seemed to be eating up hard drive space. Yesterday I noticed that I have two "almost" identical libraries...the original library, and a new one with the same name, but with the "version" number string ( I think it's a date/time stamp). Both seem to be bing updated as I work, although the new "version" library is larger, the primary difference being that any new media I add seems to be going only in this new library, although the transcoded media and render files are the same. I'm wanting to delete the "old" library, but I don't want to have it all go to hell...there don't seem to be any "pointers" in the new library to files in old library. Curious if anyone has seen this before and how to approach it.

How there became two libraries I don't know but backups are saved (depending on system configuration) in Movies > Final Cut Backups > [video file name] > [backup file name].

I suspect the backup file name has the syntax of "YYYYMMDD_HHMM_PDT.fcpbundle", where HHMM is in 24-hour clock time and PDT is the time zone the computer is set up for.

My suspicion is that one of the versions is one of the backup bundles.

For what it’s worth, I had that happen recently not long after upgrading to 10.3.2 then due to time constraints (had to upload a video "right away" and there was a crash), couldn’t determine which version was the most recent then just deleted one of them and went for it. Why do things like this happen when you most need them? No answer to that question.

Not sure if this helps as you did say it was relaunched from "version saved".

There is the old saying “If you want it bad, you get it bad.”

yeah...It's a little fuzzy, but I think I must have launched from one of the final cut Backups after the crash, but it's just strange that it's built a whole new library, and that it's writing all the optimized media and render files to both libraries, and only the new original media to one. I'll probably end up backing up the one I intend to delete before I give it a shot, just in case there's some fcpx library fairy dust attached to it.

yeah...It's a little fuzzy,....
same here

...but I think I must have launched from one of the final cut Backups after the crash, but it's just strange that it's built a whole new library, and that it's writing all the optimized media and render files to both libraries, and only the new original media to one.
That seems to be very much like what I experienced.

Because I was under pressure and in a rush I didn't remember what it was that may have initiated the problem. Fortunately all the backup file sizes were quite small.

Yeah...both of these libraries were over 700 gb, so it was starting to strain things. I ended up backing up the "old" library, and then deleting it on the system drives. Didn't seem to cause any issues.