Rebuilding Fusion drive will NOT erase the hdd?

Discussion in 'macOS' started by toke lahti, Nov 20, 2016.

  1. toke lahti macrumors 68020

    Apr 23, 2007
    Helsinki, Finland
    My ssd from selfmade fusionDrive in my cMP died. After booting to recovery mode and opening Disk Utility, It shows my fusiondrive in red. Then it says "The Fusion Drive is missing a disk" AND after "Rebuilding will erase the following disks:" and then the white box is empty?!?

    Does this mean, that it won't erase the content in hdd?

    Or is it just not able to see the name of the volume, since ssd is missing?[​IMG]
    --- Post Merged, Nov 20, 2016 ---
    :"Reverting a CoreStorage volume completely returns it to its original state, including restoring the partition type and removing encryption. And it’s non-destructive. Slick!"

  2. Fishrrman macrumors G5


    Feb 20, 2009
    I'm going to -guess- that if you let disk utility "rebuild" the fusion volume, that you're going to lose everything that was previously stored on BOTH drives (HDD portion and SSD portion).

    Hope you have a backup!

    Final thought:
    If you have another external SSD, why bother with fusion in the first place?
    Let your SSD be your SSD (boot drive), and let the HDD "be its own drive".

    You'll have to drive icons on the desktop, but it's hardly a problem to manage data between them...
  3. toke lahti thread starter macrumors 68020

    Apr 23, 2007
    Helsinki, Finland
    Why Fusion Drive Exists 101:
    With price of smallest ssd and any kind of hdd, you'll get almost same speed than with very expensive big ssd's.

    I'm not earning huge bucks. I like to use several computers. So does my family and relatives. Most of them appreciate that by knowledge and skills you can save money, even if they could spend more than needed.
    I think world is getting divided by this, some people have so much money, that they don't need to think costs and those who have so little that there's nothing to save from. No middle ground.

    I have "almost all" timemachined, but since I work with large video files from time to time, I had excluded workTMP folder from timemachine and archived video projects elsewhere.

    My last full duplicate of system disk made with ccc might be a year old. I still haven't had time to search it. I have moved since I made it...

    I guess there's no way to see from timemcahine disk what was excluded from it?

    I also guess there's no simple way to remove some big videofiles from timemachine?
    If there is, I could just let everything be backed up and manually remove video files after I have archived projects elsewhere.
  4. simon lefisch macrumors 6502a

    simon lefisch

    Sep 29, 2014
    SSDs are that expensive anymore. You can get 500GB for about $130. A "home-made" fusion drive seems to be more of a pita, but to each his own.
  5. toke lahti thread starter macrumors 68020

    Apr 23, 2007
    Helsinki, Finland
    Well, I've used to a bit bigger system disk / home directory.
    1tb os ssd costs 250 bucks. 2tb 500$.
    1tb of fusionDrive costs 70 bucks, 2tb less than hundred.
    Double that for redundance.
    (I'm gonna make raid1, since these ssd's seem to die fast without warning. With old fashioned hdd's I've used smartreporter succesfully, so when bad blocks begin to appear, I won't loose much and at least I know what I lost.)
    So for my MP, it's 500$ or 140$. Or 1000$ compared to 190$.
    For me the difference is big enough for being clever.
  6. Ebenezum macrumors 6502a

    Mar 31, 2015
    According to Apple support documentation its almost certain you will lose the information on both drives if you allow Disk Utility to repair the Fusion Drive.

    While I haven't personally used Fusion Drive I don't see how it would would be beneficial to cMP since you have multiple drive bays for drives?

    Since Apple doesn't publish details about Fusion Drive its hard to say for sure but based on the information I have found it looks quite similar to RAID-0 which means I wouldn't trust it with important data without being 100% sure all that data is backed up to at least 2 external drives.

    Purchasing couple of large drives and making regular backups would be a smart move if you wish to use Fusion Drive or RAID system. Also it might be good idea to make clones in addition to Time Machine backup, relying on 1 backup software may not be the smartest move...

    I'm not saying you have further problems with Fusion drive but if you ignore backups and have trouble with one of the drives later its likely recovering files will be very expensive.
  7. maflynn Moderator


    Staff Member

    May 3, 2009
    Deleting, or re-creating the Fusion drive is a destructive operation and you will in fact lose your data. For any work on your drive, please be sure to have a backup.

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