Interesting Core Storage quirk.

Discussion in 'OS X Mountain Lion (10.8)' started by ConCat, May 12, 2013.

  1. ConCat, May 12, 2013
    Last edited: May 12, 2013

    ConCat macrumors 6502a


    Jul 27, 2012
    In an ethereal plane of existence.
    I'm not sure what to make of this, so I'll leave it to the community to decide. I was messing around with Core Storage earlier and stumbled upon something odd. First off, here's what my LVG looks like:


    As you can see, I used three PVs of varying sizes to create this LVG. The interesting thing about this is that when I created the LV, I used "100%". Common sense says that should make the LV somewhere in the realm of the 8.8GB size claimed by Core Storage. This didn't occur however, and I ended up with the 3.3GB LV that you see. Now, this could be a bug, and if that's what I suspected I wouldn't be posting, but now look at what I found when I did "mkfile 3g testFile" on the new LV (Don't pay attention to the disk identifier. It's completely glitched for some reason):


    It almost looks like I somehow managed to trigger some sort of redundancy without meaning to. On the other hand, the missing storage could be a bug having to do with more than two drives (which is unsupported by Apple), and the write to the second disk could just be logs being written... It would make sense that Apple would design CoreStorage to write logs to any of the disks not currently being actively written to by the user (for efficiency). Each disk does contain Core Storage headers, which may all be able to contain logs belonging to any of the disks... I'm not 100% sure what I'm seeing, so I'll let you guys think about it.

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