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Old Oct 31, 2012, 08:50 AM   #1
DHKaplan
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Question Offsite Backup with OS X Raid/Mountain Lion

I currently have a hardware solution that is no longer in production (G-Safe). I would like to add another Raid 1 drive pair to my Mac Pro, so that I can periodically break Raid, swap out the 2nd drive and take that current 2nd drive off site and replace it with another brought back from offsite.

Is this a viable solution with OS X Raid?

Can you successfully remove "Drive 2" and have it retain its data, and add a new "Drive 2" that will get its data copied from "Drive 1"?

And if my "Drive 1" went bad can I get a new one of the same size and restore from "Drive 2"?

And of course, how reliable is OS X Raid on Mountain Lion?

Thanks!
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Old Nov 1, 2012, 02:50 AM   #2
kave
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No, I would not do this.
It should be no problem replacing a raid member with a new empty disk, but what happends when you get your old raid member with the current one?
Or are you going to format the old drive every time?

Raids are not for backups.

Buy two USB drives and use time machine. Now with ML you can use two different drives without problem.
This way you get a proper backup with history as well.
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Old Nov 1, 2012, 08:15 AM   #3
DHKaplan
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Hi Kave,

I really don't understand your reply. What do you mean by:

"what happens when you get your old raid member with the current one?"

I alternate drive #2. One is off site, and periodically I bring it back home and take out the current drive #2, and replace it with the new one, and take the one just removed off site again.

This is data doesn't change very much, but this way I have protection if the entire raid array gets messed up.

Thanks...

David
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Old Nov 1, 2012, 09:18 AM   #4
haravikk
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It sounds like you're talking about bringing the offsite disk and just popping it into your machine and hoping the RAID pair will rebuild from that disk, rather than the one already in the machine?


It seems a messy way to do things and I'm not sure AppleRAID will rebuild the array unless one of the disks is wiped; as a backup solution this would mean you'd actually have less redundancy while you're rebuilding the set. I dunno how G-Safe worked but it was likely a bit more sophisticated with some kind of merge/sync functionality.

Sounds to me like rsync might provide something like what you're after. You just need to create a script or AppleScript app with an rsync call inside, and use this to sync the portable drive with the local drive on any machine you connect it to. Then do the reverse when you're ready to take it somewhere else.

This way the portable drive always has the latest copy of everything, but your machines still have a copy just in case.
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Old Nov 1, 2012, 09:25 AM   #5
Aragornii
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Quote:
Originally Posted by kave View Post

Buy two USB drives and use time machine. Now with ML you can use two different drives without problem.
This way you get a proper backup with history as well.
I do essentially this but use Carbon Copy Cloner to back up to my offsite USB drive. Do you see any advantage to using Time Machine over CCC?
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Old Nov 1, 2012, 09:31 AM   #6
DHKaplan
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Thanks haravikk and Aragornii,

My hardware solution did provide for offsite backup. You remove the 2nd drive and put in a new one and it would automatically back up Drive 1 to Drive 2. Pity they stopped making it. Apple Raid does sound problematic, since I don't have a lot of documentation on it.

I'll have to keep investigating alternative solutions.

David
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Old Nov 7, 2012, 03:59 AM   #7
kave
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Quote:
Originally Posted by Aragornii View Post
I do essentially this but use Carbon Copy Cloner to back up to my offsite USB drive. Do you see any advantage to using Time Machine over CCC?
Yes, the difference is that go also get history in your backups. Let's say you corrupt a file today, you make the sync to drive1 this evening.
Next week you sync to drive2.
The week after you liked to use the file, but it will be corrupt on all three drives since you won't have history.

Time machine will give you a version from every change you make. So you can go back in time and say I need this file as it was 2.5 weeks ago or whatever.

----------

Quote:
Originally Posted by DHKaplan View Post
Hi Kave,

I really don't understand your reply. What do you mean by:


David
Well, what I mean is that you have three drives, driveA and DriveB and driveC.
Lets say DriveA is always connected. You alternate drive B and driveC.
When you replace driveB with DriveC the second time you will have different data on DriveA and DriveC. How would the raid system know which is the one you like to use?
I don't even think you can do this, but why don't you try?
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Old Nov 7, 2012, 06:02 AM   #8
DHKaplan
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Thank you Kave,

My existing hardware RAID 1 knows automatically to always copy A to either B or C which was put in slot 2. I am trying to find out if the software OS X Raid will allow you to choose how the RAID structure is rebuilt.

Thanks...

David
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