Fusion Drive and Time Capsule backup problems?

Discussion in 'iMac' started by Aluminum213, Oct 29, 2012.

  1. Aluminum213 macrumors 68040

    Aluminum213

    Joined:
    Mar 16, 2012
    #1
    I read somewhere this was going to be a problem, does anyone know more about this?
     
  2. MonkeySee.... macrumors 68040

    MonkeySee....

    Joined:
    Sep 24, 2010
    Location:
    UK
    #2
    probably best wait untill its out. Do you think Apple will say when they developed it "oh yeah, this isn't going to back up correctly. oh well" :D
     
  3. Aluminum213 thread starter macrumors 68040

    Aluminum213

    Joined:
    Mar 16, 2012
    #3
    LOL, I figured that much but I really want SSD speed but I don't want the 27' screen size so the fusion is my only option
     
  4. Dween macrumors member

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    Jun 7, 2012
    Location:
    London, UK
    #4
    I think you'll find Apple will say "You're doing it wrong" :p
     
  5. ZMacintosh macrumors 65816

    ZMacintosh

    Joined:
    Nov 13, 2008
    #5
    the only issue i could see occurring is that since its seen as one logical volume for two-drives restoring it to a single drive with lesser space might confuse people.

    I back up my SSD+HDD iMac to time machine just fine, I just dont know anything that would cause time machine to act any differently?
     
  6. timcullis macrumors member

    Joined:
    Oct 9, 2012
    Location:
    London
    #6
    Where did you read that?

    Can't see why there would be a problem; from what I understand the operating system presents the two drives to the user as a single logical volume, and would undoubtedly store it as such in Time Machine.

    This gives you the ability to backup to Time Machine from either a HDD-only system, or a SSD-only system, or a Fusion system, and to restore the backup to any of the above combinations.
     
  7. theSeb macrumors 604

    theSeb

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    Aug 10, 2010
    Location:
    Poole, England
    #7
    TM can backup all of your internal drives as long as they are formatted in HFS+. That is exactly what a fusion drive is, except it also has some algorithms running at the Core Storage layer that decide where the data is written and whether the 4 GB of cache on the SSD is used, or not. The other difference is that the fusion drive is two drives presented as a single volume to the OS, which is basically exactly what happens if you had two internal drives set up with RAID 0 or 1 using disk utility. You can back up RAID volumes with TM and you can restore back to RAID volumes using TM. There is no reason for TM to not be able to backup and restore a Mac with "fusion" drive. The only complication is what to do with the 4 GB of cache and if you're running a TM backup at the same time as a write operation is happening on your fusion drive.
     
  8. sirozha macrumors 6502

    Joined:
    Jan 4, 2008
    #8
    The problem with a restore from a Time Machine backup is where the information going to be restored - the SSD part or the HDD part of the Fusion Drive. Apple has said that the OS and all of the applications that come with the OS will be stored on the SSD portion. When you restore from a Time Machine backup made on a different Mac, the Migration Assistant should be “Fusion Drive aware” in order to place data being restored to the correct part of the Fusion Drive. So, I wonder if not only the Disk Utility, but also the Migration Assistant (and perhaps Time Machine) is/are also “Fusion Drive aware”. The normal migration path from an earlier Mac to a Mac with a Fusion Drive should be to use the Migration Assistant to bring over all applications, settings, and user data from the Time Machine backup made from another Mac to the Fusion-Drive Mac. Hopefully, Apple has thought of that and has a mechanism that restores from the Time Machine backups and places the data in the correct part of the Fusion Drive. Apple has not revealed yet how this is to be handled. The alternative to this is to install all applications on the new Fusion-Drive Mac manually (hopefully they would install on the SSD), and then use the Migration Assistant to bring over the settings and the user data from the Time Machine backup.

    Another way this could be done is that the Migration Assistant (or the Time Machine backup) places everything to the HDD during the Time Machine restore, and then the brains behind the Fusion Drive gradually repositions the applications and the user data to the SSD portion of the Fusion Drive as applications are being used. This process may take weeks or even month to relocate the proper applications from HDD to SDD based on the algorithm that Apple has programmed into the Fusion Drive technology. That’s probably the reason why Apple pre-installs all standard applications that come with the Fusion-Drive Mac onto SSD at the factory.
     
  9. theSeb macrumors 604

    theSeb

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    Aug 10, 2010
    Location:
    Poole, England
    #9
    I can only speculate, but from a logical point of view, it makes sense to keep all of the fusion drive stuff within fusion drive, without having to change how TM or Migration assistant work. The fusion drive stuff will be keeping track of where all of the files are and on which drive. So that means it’s keeping an index of all of this. It would make sense that some new “fusion” hidden fields have been to Spotlight, since it already keeps an index of all of the files, or another index has been created. Since the index is just a file, it will also be backed up. Then when stuff is being restored to a fusion drive, the fusion drive algorithm within Core Storage simply looks at the index in the backup and restores the files to the appropriate drive within the fusion drive array.

    This would be a good use of encapsulation since apps like TM or Migration Assistant should not care about the underlying drive structure. It’s what happens when you’re running software RAID and I would expect Fusion drive to encapsulate all of this stuff in the same way. Having to change TM/Migration Assistant/Finder and so forth specifically to work with fusion drive is nonsensical.
     

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