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Time Machine and RAID1

dangerly

dangerly

macrumors regular
Original poster
Oct 27, 2009
151
5
European Dis-Union
Hello,
have a question regarding Time Machine and the possibility to use two external drives set up as RAID1.
Can i set up two external drives as RAID1 and then have Time Machine back up on one of this drives?
Will the second drive in the RAID be utilized to restore the Mac with no problems, that is will the second drive be recognized by Time Machine as a valid drive to restore files, applications, or an entire Mac?
Thank you
 
I have RAID setup on both my DAS and NAS and both have worked fine for Time Machine.

As for restoring off the second drive of the RAID. Perhaps I'm misunderstanding you, but RAID 1 is mirroring so both drives have the same data. It appears to you in Finder as a single drive when you set up a RAID array.
 
maflynn said:
I have RAID setup on both my DAS and NAS and both have worked fine for Time Machine.

As for restoring off the second drive of the RAID. Perhaps I'm misunderstanding you, but RAID 1 is mirroring so both drives have the same data. It appears to you in Finder as a single drive when you set up a RAID array.
Click to expand...

Thank you.
Yes i want the drives to be mirrors, same data on both, and they will be used only for Time Machine.
I just wanted to be sure that i would be able to use any of the two drives in case i had to restore files or an entire Mac.
 
Either I'm misunderstanding you, or vice versa.

There is no "any two" drives in a raid array when restoring a backup. You only see a single volume in the Finder (or Time Machine preference). The RAID controller takes care of mirroring the drives when writing data.

I use a Drobo Mini with 4 drives. I see only a single volume for my TM backups, not 4 drives that are mirrored (technically one is for parity but you get my point)
Drobo_TM.png
 
maflynn said:
Either I'm misunderstanding you, or vice versa.

There is no "any two" drives in a raid array when restoring a backup. You only see a single volume in the Finder (or Time Machine preference). The RAID controller takes care of mirroring the drives when writing data.

I use a Drobo Mini with 4 drives. I see only a single volume for my TM backups, not 4 drives that are mirrored (technically one is for parity but you get my point)
Image
Click to expand...

What i want to be sure of is:
if i have to restore an entire Mac (new Mac or after a new install of OSX) will my RAID array be recognized and correctly used?
My external HDDs are two separate Lacie 3Tb.
 
dangerly said:
What i want to be sure of is:
if i have to restore an entire Mac (new Mac or after a new install of OSX) will my RAID array be recognized and correctly used?
Click to expand...
Yes, if you have an external drive enclosure capable of RAID, then it will be recognized by the OS.

My external HDDs are two separate Lacie 3Tb.
Click to expand...
And once you build a RAID array, you will no longer have 6TB of storage across two hard drives. Instead you'll only see one 3TB RAID volume.

How are you planning on implementing the RAID array?
 
maflynn said:
Yes, if you have an external drive enclosure capable of RAID, then it will be recognized by the OS.


And once you build a RAID array, you will no longer have 6TB of storage across two hard drives. Instead you'll only see one 3TB RAID volume.

How are you planning on implementing the RAID array?
Click to expand...

I don't have an external enclosure, i have two external HDDs.

I want to set them as RAID1 to use with Time Machine, so i will have two copies of my backups, so the Mac's internal drive doesn't have to work twice.

But, if i buy a new Mac and want to restore from the external drives set as RAID1, will it work fine?
 
dangerly said:
But, if i buy a new Mac and want to restore from the external drives set as RAID1, will it work fine?
Click to expand...

If you set up a RAID array in OS X, and you connect those two drives to a new Mac, the new Mac will see the RAID array. The configuration information is stored on the drives, not the computer.

A.
 
dangerly said:
I don't have an external enclosure, i have two external HDDs.

I want to set them as RAID1 to use with Time Machine, so i will have two copies of my backups, so the Mac's internal drive doesn't have to work twice.

But, if i buy a new Mac and want to restore from the external drives set as RAID1, will it work fine?
Click to expand...

I understand why you are doing this, but it's a flawed strategy, because there is a single point of failure, Time Machine itself. It can and has failed in the past due to various bugs or user error. Has happened to me.

You would be much better protected by using TM to backup to one drive, and an entirely separate method, let's say carbon copy cloner, to backup to the other separate drive.

And don't omit taking offsite backups from time to time.
 
^^ That's not bad advice but having RAID protection isn't all that bad either.

Here's my backup strategy.
I use a Drobo Mini DAS that uses RAID 5 (mirroring + parity) though they modified and its pretty much proprietary but in the end its a hybrid RAID 5 setup.

I also use Carbon Copy Cloner to image my drive on a different external drive. Finally, I have a portable drive that gets images every few weeks and I take that offsite.

I think using RAID for a Time Machine backup is not bad as it provides data redundancy on your backup and if one drive fails your backup is intact.

NAS and DAS units have become very popular for this very reason, and the OP is on the mark looking to improve his data protection.
 
maflynn said:
^^ That's not bad advice but having RAID protection isn't all that bad either.
Click to expand...

I agree overall, the more backups the better, but my essential point is that if backing up to only two drives,as the OP is, then mirroring is a much less robust solution than is two separate methods one to each drive.
 
dangerly said:
Hello,
have a question regarding Time Machine and the possibility to use two external drives set up as RAID1.
Can i set up two external drives as RAID1 and then have Time Machine back up on one of this drives?
Will the second drive in the RAID be utilized to restore the Mac with no problems, that is will the second drive be recognized by Time Machine as a valid drive to restore files, applications, or an entire Mac?
Thank you
Click to expand...

Completely unnecessary. You can select two drives in Time machine and it will ping-pong between the two giving you two complete backups. You get the added benefit of not dealing with Raid complexity.
 
ssls6 said:
Completely unnecessary. You can select two drives in Time machine and it will ping-pong between the two giving you two complete backups. You get the added benefit of not dealing with Raid complexity.
Click to expand...

Correct, but the Mac's internal drive has to work twice as much.
 
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