Move Time Machine data to a Drobo

Remember, even Drobo's can die. Make sure your files are in at least three different physical locations, one of which preferably off-site.If Santa treated you particularly well this season, or you have put some of your savings to good use, chances are that you have a brand-new Drobo looking at you right now. Meanwhile, your Mac is happily making Time Machine backups to that trusty old local USB disk. So you want to use that new Drobo for Time Machine backups, but don’t want to loose history? Here’s how (baby steps, no tools required, screenshots included):

  1. Connect the Drobo (in my case a Drobo FS) to the network and configure an Administrator password for it. You should now have a working Drobo, with at least 2 drives in it, and it shares a “Public” share on the network.
  2. Make sure that the free space reported by the Drobo Dashboard is at least as big as your old USB Time Machine drive. Add drives to the Drobo as needed.
  3. In the Drobo Dashboard, click on “Advanced Controls”, go to the “Tools” tab, click on “Settings…” and then select the “Shares” tab.
  4. Create a new user for your Time Machine backup. It’s important to create a non-admin user to keep your data safe. Trust me, you’ll thank me later.
  5. Create a new Drobo share (the “+” on the bottom left), give it a meaningful name and select “Enable Time Machine on this drive”. Be careful in choosing the size, you can’t change this later!
  6. Remove “Everyone” from the allowed users for this share (the “-” bottom right) and add the user you just created (the “+” on the bottom right). You should now have something like this:Create Time Machine share on the Drobo FS screenshot
  7. Close Drobo Dashboard, we won’t be needing it anymore.
  8. Open System Preferences on your Mac, and select “Time Machine”
  9. Click on the “Select Disk” option. Don’t worry, we’re not damaging or loosing your existing backup by doing this.
  10. In the popup, you’ll see your newly created Time Machine share on the Drobo. Select this share and fill in the Userid and Password you just created on the Drobo.Select Drobo Time Machine share
  11. Wait for Time Machine to start, or force it by using the “Backup now” menu option. Time Machine will first try to create a sparse bundle and calculate what to back up. As soon as you see the backup starting (the “zebra” stripes turn into a normal progress bar), click on the cancel button. We only used Time Machine to create a sparse bundle with the correct settings.
  12. In System Preferences, switch Time Machine off.
  13. Go to the Drobo Time Machine share you just created and mount the sparse bundle you see there.
  14. Open Disk Utility and select the USB Time Machine disk.
  15. Click on “Restore” and drag the partition of the old USB Time Machine drive to the “Source” box. Drag the partition on the mounted Drobo Time Machine disk to the “Destination” box. Double check my screen shot, it’s important to get this right. Drag the partitions, not the disks itself. If you’re not able to drag the disks as described, you may want to unmount your old Time Machine drive, remount it, and restart Disk Utility.Drag partitions in Disk Utility
  16. Make sure “Erase Target” is selected and press “Restore”. Disk Utility may ask for your password.
  17. Prepare for a long wait. If you have more than a 500GB backup drive, you wish you had invested in Gigabit Ethernet right now (yes that speeds it up tremendously). My restore of 800GB over a 100Mb network took more than 2 days.
  18. Once the process is finished, do not forget to switch Time Machine back on in the System Preferences.

That’s it. Time Machine will automatically mount the Drobo Share if needed. The first backup will take a bit more time, I think Apple built in a file check to see if the backup is still ok after moving it to another disk.

Tip 1: Keep your old USB Time Machine disk next to the Drobo, even if you have an empty slot. By doing this, you can instantly replace a faulty drive without running to the store. Always keep a spare!

Tip 2: Storing data on your Drobo, and then backing up to a Time Machine bundle on that same Drobo is not a backup. A file is only safe if it is stored in 3 different physical locations, one of which is preferably off-site.

Happy Drobo days!


20 Responses to Move Time Machine data to a Drobo

  1. Terry Allan says:

    Thank you for posting this article. Am I correct in saying however that Disk Utility will not see the Drobo FS? I think that Disk Utility can only connect to directly connected discs. I note from your diagram that your destination was a Mac Mini and not a Drobo FS.

    I am having a great deal of difficulty in creating an initial Time Machine backup on my Drobo FS and so a way of taking an existing 2.7TB backup from a Sonnet Array, converting it to a sparse bundle or as you have done copy it in to an existing sparse bundle on a Drobo FS would be very useful.

  2. rolfje says:

    Hi Terry,

    Thanks for commenting, glad to help. I have the Drobo FS, and this drobo does not have the USB option. Everthing I did was exactly done as in the article, and 100% over Ethernet. If you look carefully at the diagram, it shows that de DMG just is mounted on the Mac mini (see step 13), but the data resides on the Drobo. Just like any DMG mounted over the network.

    To be clear, I did not “convert a disk to a sparse bundle”. I had Time Machine create a Sparse Bundle on the Drobo FS, then used disk utility to copy from the physical old disk into the newly created Time Machine sparse bundle.

    As long as you pay attention it doesn’t destroy your old Time Machine drive, as your copying from it, not to it. I took great care in describing the process as detailed as possible, I really hope it works for you too.

    It does take quite some time, I’d advise on getting a Gigabit network first.


  3. Terry Allan says:

    Many thanks for response

    Yes, I did understand what you had done with respect to the creation of the sparse bundle. What I had misunderstood was how you mounted the existing backup in Disk Utility. Now I understand.

    My existing backup is 2.7TB and it exists on a Sonnet Fusion D500P with 5x1TB drives in it. I will try your procedure if my current backup to the Drobo fails. I will let you know how I get on.

    Your article will I am sure be of use to many people.

    Thanks again


  4. Terry Allan says:

    Hi Rolf

    I followed your instructions and the process of copying was fairly rapid. Disk Utility then went into verification mode. That process seemed to be making no progress at all even after 12 hours. After a little thought and investigation and examination of the options I stopped the verification. This I had hoped would not affect the integrity of the copy but I was wrong. Clearly Disk Utility needs to tidy up at the end of the process and I prevented it from doing that.

    I discovered (or so I thought) that Disk Utility preferences permits me to opt-out of Verifying using Checksums. I thus deselected Verify Checksums, deleted the Drobo Share, created a new Drobo Share (Time Machine enabled), created a new sparse bundle as per your instructions and finally I invoked the Disk Utility Restore again, as per your instructions.

    The copy process took a very reasonable time through my mega bit switch (<15 hours) but unexpectedly the system then went straight into verification mode again despite the opt-out. At the moment I am sitting with what looks like a stalled process.

    Did your system go through verification and how long did it take? Any ideas, advice and thoughts would be most welcome.

    Many thanks


  5. Terry Allan says:

    Hi again Rolf

    Just thought I would provide an update on the process. The verification process hasn’t in fact stalled. It has just given me an estimate of 61 days and 12 hours on the progress bar in Disk Utility.

    Hopefully this is inaccurate and that estimate will reduce rapidly as the process proceeds. I will give it a few more hours.

    Best wishes


  6. Terry Allan says:

    Update again Rolf

    As was clear from my previous post the verification process had to be stopped – just from a time perspective. Stopping, however, in an acceptable and orderly manner – using the stop button – was going to take as long as the verification. After 24 hours I just had to abort it. I had hoped that by stopping it in an orderly manner, I could then save whatever had been transferred. No such luck though when I had to abort the process.

    I suspect that there is something ‘wrong’ with my Drobo or the interaction of the Drobo FS, Time Machine, my hardware and my operating system and that is what led to me trying this approach in the first place. I have been in contact with Drobo Support for a considerable number of weeks with no positive outcome yet, despite already having had one replacement Drobo sent.

    Thanks for the idea, this blog post and for your comment.

    Best wishes

  7. Terry Allan says:

    I forgot to say that I do have a Gigabit switch and LAN.

  8. rolfje says:

    Hi Terry, sory for the late reaction, thanks for all the updates. I seem to remember that the verification process was very slow on my copy aswel. I “only” had to copy 800GB, and that took 2 days.

    I guess the migration process to a Drobo is not the quickest of all jobs. In an effort to help, is it an idea to see if you can slim down your backup by throwing away older backups you don’t need? Or maybe excluding folders with temporary large stuff in it?

    As for the process itself, I’m afraid I don’t know any tricks to speed things up. I seem to remember that there is also somebody who did the same trick with Carbon Copy Cloner or Super Duper. I googled but I can’t find helpful info other than flimsy forum posts with more questions than answers I’m afraid.

    Maybe you want to re-start the process just before you go on a long weekend or so. 😉

  9. Trevor says:

    Hey Rolf,

    I hope you don’t mind answering a questions of mine. I upgraded form the Drobo to the Drobo FS as I was tired of manually deleting old Backups and wanted Time Machine and Drobo to finally run in concert with each other. Unfortunately, my 10TB Drobo is full and it is now telling me “Unable to complete backup. An error occurred while creating the backup folder.”

    Any ideas on why Time Machine isn’t managing this Drobo properly?

    Thanks for your time.


    • rolfje says:

      Hi Trevor,

      Good news and bad news. First the good: Moving to the DroboFS will solve the problem you have right now. The bad news: You have to do some backup grooming and planning yourself.

      The reason for your problem is that the “old” Drobo is full, yet it reports to your Mac that it is “16 TB” in size. That’s why Time Machine tries to make a backup and then fails.

      If you look into [Old Drobo]/Backups.backupdb/[Your Mac’s name]/[hard drive name] on the Drobo, you will find all backups it has made. If you sort Alphabetically, the oldest ones will be on top.

      I haven’t tried this, but theoretically it should be possible to delete the first few backups. This should do the same as Time Machine would do when grooming the old backups.

      This article explains why you are able to do that, and what happens to the files in your backup:

      Now that you’ve got room on the old Drobo, Time Machine should be able to complete it’s backup.

      Now on your new Drobo FS, you have the possibility to create a Time Machine volume. It will have a fixed size. You have to be careful when picking the size because you can’t change it later (why that is, beats me and I hope Drobo will fix that). Because the Drobo FS reports this size to Time Machine, Time Machine will be able to detect when the “Drive” is “Full”, and automatically start deleting old backups.

      I’ve choosen my DroboFS Time Machine volume to be 3 times the size of all the stuff I want to back up. 2 times is advised but I went bigger because I might want to add another external Drive to the Mac without having to migrate the whole Time Machine volume again.

      I hope this helps, Cheers,

  10. Terry Allan says:

    Hi Rolf

    I had a fairly frustrating time with my Drobo FS until I finally accepted that it was not going to do what I wanted. I then implemented a less Drobo demanding strategy with which the Drobo FS could cope. It carries on in the background now doing what it is asked to do ‘without many complaints’.

    The support from couldn’t help me and in the end I think that I was being offered an eSata Drobo as a replacement for my Drobo FS. I declined the offer as it did not do what I required.

    The whole process was so frustrating that I recorded it on my site for the interest of others.

    Best wishes


  11. Trevor says:

    dude – you’re great. Let me scour over this and make it happen – I’ll get back to you with the word.


  12. Trevor says:

    Hey Rolf,

    I’m only the first paragraph in and I see I should have clarified. I’ve had the FS for a year now. It has done months of successful backups. But the Drobo FS is only now full and with all the hype to work well with Time Machine, it appears to be behaving the same way as the predecessor. I’m sure I’m missing something – just can;t figure it out. I’ll continue on with your post.

    and thanks again.


  13. rolfje says:

    Hi Trevor, I’ve checked my Drobo FS Time Machine Volumes (multiple macs backing up to that) but it’s not full so Time Machine hasn’t removed old backups yet. Therefore I can’t prove to you that it works or do tinkering to see if I can reproduce your problem.

    Are you sure that the size of the Time Machine volume you created in Drobo Dashboard is smaller than the total size of the disks you have in your Drobo?

    No need to thank, my philosophy is that I should help “the Internet” as it helps me. And besides, happy people make me smile. 🙂

  14. […] moved all backups to the Drobo. Life would be good. Or so I […]

  15. Pete says:

    Can I ask a potentially silly question. My iMac HDD died yesterday, luckily it’s all backed up on my Drobo FS! However, when I use the OSX Snow Leopard installation disc to restore from a System Backup of Time Machine, it cannot see the Drobo FS, whether Drobo FS is plugged into my AE or directly into the iMac. Guess it needs to be mounted, but how the heck do I do this from the installation disc?
    Surely this is a common issue if you need to do a System Restore when a HDD on your iMac dies, but I can’t find any instructions on how to mount the Drobo so a System Restore can be done.
    Can anyone help?

  16. avieong says:


    Thanks for this most helpful post.
    I’ve followed your instructions very closely & have succeeded in all the steps, only to be faced with the following error:

    Restore Failure

    Source volume is read-write and cannot be unmounted, so it can’t be block copied.

    Where to from here?!

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