My new best friend, the mirror

So timemachine tanks every month or 2, says it wants to rebuild the whole backup file again which is an uber pain. So, before it can create a new file it has to delete the original of course which means you no longer have a backup until its complete again and a complete backup takes about 24 hours (almost 400gigs). I’ve blogged on time machine before and its issues, but to remedy this consistent issue I finally realized a good way to get a copy of the data without having to create a new backup file with something other than time machine.

With my Netgear Stora, granted not the most popular unit and definitely a consumer level only unit, I’m able to create a mirror, aka, RAID1

In RAID 1 (mirroring without parity or striping), data is written identically to two drives, thereby producing a “mirrored set”; at least two drives are required to constitute such an array. While more constituent drives may be employed, many implementations deal with a maximum of only two; of course, it might be possible to use such a limited level 1 RAID itself as a constituent of a level 1 RAID, effectively masking the limitation.[citation needed] The array continues to operate as long as at least one drive is functioning. With appropriate operating system support, there can be increased read performance, and only a minimal write performance reduction; implementing RAID 1 with a separate controller for each drive in order to perform simultaneous reads (and writes) is sometimes called multiplexing (orduplexing when there are only two drives).

Once the mirror is in place and a full backup is there, I can break said mirror, take one drive off site, plug in a fresh drive and rebuild that mirror again to have a fully functioning mirrored NAS again. Effectively, any time Time Machine has issues, i can swap in / out the third drive I have and store the most recent copy somewhere else.

Currently I have 3 x 1 TB drives (3.5 inch, 7200 RPM, two from Seagate and one from samsung). In the mirror I have total backup space of just under one terabyte which is adequate since I”m mainly backing up our macbook drive which is 500gigs.

I should be good with this setup I think even when I get a 1 TB drive in the macbook (which is something I can’t see anytime soon – I have 75 gigs left on the macbook, so with just pics and movies, it will be another year or so anyways).

So i don’t know why I never thought of breaking the mirror and using that as a copy… Works great! This total backup solution now has cost about $450. but better that than losing it all!

I walk through the process in this youtube video:

[youtube 3uRHxjmMdBM]


The process for the next guy, and the next time I restore OSX or break the mirror is this:

  1. Do one last full backup before restoring (or if your drive crashed, hope the last backup was good and recent. )
  2. Restore from TimeMachine as per documented by Apple using timemachine
  3. Now TimeMachine will need to run again, it will potentially complain of no space if your drive is out of space, the old TimeMachine backup after a restore is totally invisible to the new install. TM will not reuse it, TM will not even SEE the 400 gigs of backup that was used just minutes ago to restore the system so that sparsebundle of a backup is completely dead weight and taking up space now. You’ll need to backup to a fresh sparse bundle
  4. Ensure you have a secondary backup, I use SuperDuper to keep another clone backup along side TMs file on my Stora
  5. In Stora preferences click ‘Wipe’ button under the backup section. This ONLY wipes the backup partition of the drive so it won’t touch your super duper backup. TM requires its own partition, or at least Stora does that for it. Once wipe is complete:
  6. Allow TM to fire and run till the end
  7. Break the mirror. After TM is completed, go to backup in preferences on the store. Click ‘eject’ on one of the drives’
  8. Remove the drive (this is your ‘off site’ backup drive). It has one complete copy of your latest backup and your secondary backup file.
  9. Insert new or used same size drive (I rotate 3 one terabyte drives for total mirrored space of 1 terabyte, my drive backups are aboue 430gigs each currently)
  10. Start up Stora
  11. In preferences click ‘configure drive’. The system automatically knows what the new drive is even if the new drive has data on it. It will wipe that ‘new’ drive and start syncing the drives all over again to repair the mirror
  12. And thats it. You can now rotate 3 drives in your Stora unit ensuring good protection of your data. You’d need 3 simultaneous failures to lose all your data (or a horrible bug / malware that ate through your data :S). A house fire for one would cause issues for all 3 for sure, so its always best to have one outside in a shed or something or take one to your locker at work for example.

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2 thoughts on “My new best friend, the mirror

  1. Hi,

    I don’t know if you are going to read this, as this post is almost 4 years old, but maybe you will and could help me with my question.
    I am using a stora again. Used it in the past with one drive and backed up some important files. Never used it again since then.
    Now I want to add a second drive (no mirror) but the message says, that it will delete all files. Will this only be for the “new” drive or wil the first drive be deleted, too?
    I don’t want to try unless I am 100% sure…

    Thank you.

  2. great question! i was always a little unsure of what it will do, even having removed and added drives many time. it never gives you real confidence in what its about to do. I would say it will probably only delete from the new drive, it should know. That being said, you should buy a USB backup drive and copy your data over to it, then add the new drive. you can get usb drives for cheap and its a good extra backup. You could remove the existing one and add the new one, boot it up, let it do its, thing, then add the original drive back. hope that helps. Sorry I can’t be more confident! I”e never used JBOD config.

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