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Question

Block Copy + SSD + Casper?

  • August 1, 2012
  • 3 replies
  • 25 views
ImAMacGuy
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So i was reading another thread https://jamfnation.jamfsoftware.com/discussion.html?id=3792 and @rpg mentioned something about block copies & ssd's dont play well together but didn't elaborate.

The reason I ask is because i just set our finalized "standard" MBP as the Retina w/ SSD.

What issues am I going to run into because of this? Was this resolved in Casper 8.6? I guess I haven't had a problem with the MBAirs, but I have noticed that since I made a custom NBI with the 2012 MBAirs if I diskutil eraseVolume on the drives I can only do one partition, then it gives an error about not able to unmount the drive when I try to do another partition. If I reboot then I can do the 2nd partition.

    3 replies

    J
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    • jarednichols
    • Valued Contributor
    • August 1, 2012

    I was working with Nate when that was all going down so I may have a little info on this. If memory serves correct (Nate correct me if I'm wrong) I think this had to do with the full disk encryption that would have come afterwards due to the way that SSDs differ in function from spinning disk.

    G
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    • gknacks
    • Contributor
    • August 1, 2012

    On the MacBook Air having the issue open terminal and use the command:
    mount

    If one of your partitions comes back as /private/var/netboot (i think that's it) then your shadow file is on that partition you can't eject and your netboot isn't really running diskless. We had the same issue, look for the other thread on 10.8 diskless netboot as I posted the fix we used there.

    R
    Forum|alt.badge.img+13

    jared, that's about half of the story, as far as i can tell. the issue may be that when doing a block copy, asr doesn't leave any free/slack space on the volume. on SSDs, that may cause degraded performance. on top of that, if you encrypt the whole disk, you effectively map all the blocks, potentially further degrading performance. i haven't seen this in practice myself, but others here with possibly a more discerning eye or more demanding needs have. i'll see if i have any other details in my notes that could be helpful. there are a number of variables, including TRIM support and a bunch of other stuff specific to drive controllers.

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