09-01-2010, 10:14 PM

Hello...

I have:

-MacBookPro - OS X 10.6.4 - with 1-TB 2.5" Hard Drive.
-A 1-TB 3.5" External USB Drive.
-Master Hard Drive booting and working fine.
-USB Hard Drive is attached and formatted with no problems.

My intention:

-I have the will to use RAID-1 as a solution to mirror the master Hard Drive (the only Hard Drive in any Mac Book Pro!) to the 1-TB USB Hard Drive.
-I read that I can do that using the MacBook Pro Recovery CD. This is with using the RAID tab in the Disk Utility.(No problem so far).

Question/Doubt:

-It is a Laptop Computer, and I take it with me everywhere; normally, I would disconnect the computer from the USB hard drive when I am on the move.
-I would use the computer at work or anywhere else; so, data would be accessed, modified, added, or even deleted!
-Now, if I connect the computer back to the USB Hard Drive, what will happen?
-How would the two RAID-ed hard drives behave?
-Would the Laptop recognize the Laptop Hard Drive as a master/source and the USB Hard Drive as the destination?
-How would the RAID-1 setup treat "rebuilding" for the two drives?
-What would be copied to the Destination drive? all data? changes?
-Lastly, remarks and suggestions are appreciated.

Thank you...


Ahmad

09-01-2010, 10:50 PM

Not sure that a RAID1 setup is what you actually want. It's just not intended to be used in this manner. It's really intended for always-on servers that have to have redundancy in the event a mechanism fails. Constantly breaking the RAID set by separating the second disk is going to mean constant rebuilds - and with software RAID, that's going to lead to performance problems and potential data integrity issues.

I'm not sure what lead you to the conclusion that RAID1 was the right solution given your circumstances, but I would recommend simply using Time Machine with your external. Each time you plug it in, it will automatically backup everything that has changed on your system. And if you happen to leave it plugged in and are working on your Mac, it will instantly backup any changes that are made. If there's a failure, you can easily recover from it with very little hassle.

09-02-2010, 09:24 AM

Hello,

Thank you for the answer.
I am familiar with the method you described.

Let me revise the question:

Since the option is available in OS X and we can RAID-1 the internal(Master Bootable) drive with an external one, and I assume that the laptop is always attached to the computer from booting until shutting down the computer....

Now, if the external drive's cable accidentally gets disconnected and I boot up the laptop without the second hard-drive being attached to the laptop.

-What would happen?
-Would the Laptop boot normally?
-If I link the USB Drive again, should I rebuild the RAID-1 chain again using Disk Utility after booting from the recovery CD?

This would answer my question clearly.

Thank you,,,

Ahmad

Originally Posted by cwa107

Not sure that a RAID1 setup is what you actually want. It's just not intended to be used in this manner. It's really intended for always-on servers that have to have redundancy in the event a mechanism fails. Constantly breaking the RAID set by separating the second disk is going to mean constant rebuilds - and with software RAID, that's going to lead to performance problems and potential data integrity issues.

I'm not sure what lead you to the conclusion that RAID1 was the right solution given your circumstances, but I would recommend simply using Time Machine with your external. Each time you plug it in, it will automatically backup everything that has changed on your system. And if you happen to leave it plugged in and are working on your Mac, it will instantly backup any changes that are made. If there's a failure, you can easily recover from it with very little hassle.

09-02-2010, 09:44 AM

Originally Posted by AhmadMarafi

Hello,

Thank you for the answer.
I am familiar with the method you described.

Let me revise the question:

Since the option is available in OS X and we can RAID-1 the internal(Master Bootable) drive with an external one, and I assume that the laptop is always attached to the computer from booting until shutting down the computer....

Now, if the external drive's cable accidentally gets disconnected and I boot up the laptop without the second hard-drive being attached to the laptop.

-What would happen?

The mirror would be broken and remain that way until you rebuild it.

-Would the Laptop boot normally?

It should, yes.

-If I link the USB Drive again, should I rebuild the RAID-1 chain again using Disk Utility after booting from the recovery CD?

I'm not certain if the software RAID will rebuild automatically or whether you would have to force it. Pretty sure you will have to manually initiate it.


Good luck. Software RAID, in general, sucks. It's not reliable and it's slow. When you use it in a manner for which it wasn't designed, you can expect those attributes to be multiplied significantly. I don't mean to rain on your parade, but with decades of managing servers under my belt, I want to make sure you are well-warned.