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ibook_steve · Oct 24, 2009, 03:18 PM

It's interesting that another topic about RAID was just started, but mine is different.

I have an external 1 TB OEM drive in a USB drive case that has a TON of stuff on it. With my luck with drives lately, I'm paranoid about it and want to back it up to a real external drive instead of something I put together. To that end, I purchased a Samsung STORY external drive from Newegg (very good reviews for it there). Now I need to figure out how I should do this.

1) Time Machine: I cannot find a good guide anywhere about how to backup one external drive to another with TM, if that is even possible while still backing up my internal drive on my MBP to a third external drive. Thoughts?

2) RAID 1: This is what I'm thinking about. However, I started setting the RAID up in Disk Utility, but there is no option to set what the initial "master" drive is in the array (only Spare or Slice; I presume both drives would be Slice). How do I know that my drive with stuff on it will get mirrored to the new drive instead of the new empty drive wiping out my stuff on the older drive?! Or is the idea that I have to start with 2 empty drives?

Please help a RAID noob!

Steve

mduell · Oct 24, 2009, 04:53 PM

Originally Posted by ibook_steve

I have an external 1 TB OEM drive in a USB drive case that has a TON of stuff on it. With my luck with drives lately, I'm paranoid about it and want to back it up to a real external drive instead of something I put together. To that end, I purchased a Samsung STORY external drive from Newegg (very good reviews for it there). Now I need to figure out how I should do this.

What? Unless you're monkeying around with a soldering iron there's no difference between the external drive you assemble and the one you buy preassembled. I don't know what you're trying to imply with "real" in that sentence, it's not like the preassembled drives have native USB/FW interfaces

Originally Posted by ibook_steve

1) Time Machine: I cannot find a good guide anywhere about how to backup one external drive to another with TM, if that is even possible while still backing up my internal drive on my MBP to a third external drive. Thoughts?

Time Machine supports an unlimited number of source volumes but only one target volume.

Originally Posted by ibook_steve

2) RAID 1: This is what I'm thinking about. However, I started setting the RAID up in Disk Utility, but there is no option to set what the initial "master" drive is in the array (only Spare or Slice; I presume both drives would be Slice). How do I know that my drive with stuff on it will get mirrored to the new drive instead of the new empty drive wiping out my stuff on the older drive?! Or is the idea that I have to start with 2 empty drives?

Why do you think RAID1 is what you want? The advantage of RAID1 is high availability; great for servers where you don't want users to notice any failures. But there are better schemes (incremental backup, etc) for desktop users.

The process of initializing a RAID array will render all data on the disks involved unusable. There is no master, only peers.

ibook_steve · Oct 24, 2009, 05:09 PM

OK, thanks for not answering my question.

By "real", I mean that recently many of the OEM bare drives I've put in cases have failed, whereas complete external drives have had no problems for me whatsoever. In either case, that doesn't matter. I want to know the best way of backing up my external drive to another drive.

You mention "incremental backup" then you don't tell me how to do it.

Thank for you telling me that setting up RAID 1 would erase my full drive. That actually was helpful.

Can somebody else help me with this?

Steve

reader50 · Oct 24, 2009, 05:29 PM

You could use Disk Utility to clone the old external to the new one. Use the "Restore" tab. Likewise, you could use the Finder to select all - copy all to the new drive. The disadvantage is that it's a one-time backup done manually. No further updates until you do it again.

A RAID-1 solution protects you against a single drive hardware failure, but not against user mistakes. ie - if one drive lets the smoke out, your date remains on the other drive. Excellent. But ... if you accidentally (or the toddler, or the housecat - whoever) delete your essential work files from the RAID volume. In such a case, the data will faithfully be deleted from both hard drives in the mirror set.

Likewise RAID-1 does not protect against directory corruption. It just keeps both drives identical. The other RAID levels are not much different - they can offer greater speed, capacity, or protection against more than one drive hardware failure. A real backup needs to be separate, to protect against user action and OS issues.

If you have a 2nd partition, you could install OSX on it. Then boot into it every few days. Use Time Machine in the extra partition to backup the one external to the other external. Leave the 2nd external turned off in the mean time to save energy, wear & tear ... and to keep anything/anyone from messing with your backup in the meantime.

pra9ab0y · Oct 24, 2009, 05:40 PM

I'll be following this as its something I also need to get working!

ibook_steeve has said he wants to back up 1 external to another. therefore meaning that the system files won't be needed for the backup! - Am I right?, If not! sorry...

Also using the time machine feature on a mac doesn't save the folder structure correctly.
I would reckon like myself ibook_steve wants a system that will allow him to use the external like a normal external discs. Having folder trees and stuff and then just have the 2nd external mirror the 1st?

ibook_steve · Oct 24, 2009, 06:01 PM

Exactly. I basically want Time Machine for my external drive, which does not have an OS on it. Just my stuff. However, if this is not possible, as it now sounds like, and RAID setup will wipe my original drive, it looks like I'm going to have to go manual.

Unless anybody has any other ideas.

Steve

reader50 · Oct 24, 2009, 06:31 PM

My 2nd partition idea won't do what you need? Basically, it gives you a 2nd instance of TM to handle the external drive.

Main Partition TM instance - backs up everything except the external.
2nd Partition TM instance - backs up first external to 2nd external.

Assuming the stuff on the external isn't changed much, there is very little risk in only backing it up every few days.

pra9ab0y · Oct 24, 2009, 06:43 PM

Originally Posted by reader50

My 2nd partition idea won't do what you need? Basically, it gives you a 2nd instance of TM to handle the external drive.

Main Partition TM instance - backs up everything except the external.
2nd Partition TM instance - backs up first external to 2nd external.

Assuming the stuff on the external isn't changed much, there is very little risk in only backing it up every few days.

He only wants to back up the external. I think.

ibook_steve · Oct 24, 2009, 07:08 PM

I'm already backing up my internal drive to another TM drive. While your idea would work, I have so much running all the time that rebooting just to let TM run for the external drive would be a major chore.

Now that I'm thinking about it a bit more, if OS X only recognizes one TM volume at a time, if I disconnect my main TM drive (the one that backs up my internal), then switch the TM volume over to the new external and change the TM settings to not backup my internal, wouldn't that do the trick? Granted, I'd have to keep switching my TM settings back and forth, but I don't need to backup the external drive as much as the internal.

Hmmm....

Steve

mduell · Oct 24, 2009, 07:20 PM

Originally Posted by pra9ab0y

ibook_steeve has said he wants to back up 1 external to another. therefore meaning that the system files won't be needed for the backup! - Am I right?, If not! sorry...

Also using the time machine feature on a mac doesn't save the folder structure correctly.

What?

Originally Posted by ibook_steve

I want to know the best way of backing up my external drive to another drive.

You mention "incremental backup" then you don't tell me how to do it.

Originally Posted by ibook_steve

Exactly. I basically want Time Machine for my external drive, which does not have an OS on it. Just my stuff. However, if this is not possible, as it now sounds like, and RAID setup will wipe my original drive, it looks like I'm going to have to go manual.

If you don't have one drive large enough to act as the TM target, then you could use rsync/rdiff between the two external drives.

Originally Posted by reader50

My 2nd partition idea won't do what you need? Basically, it gives you a 2nd instance of TM to handle the external drive.

Main Partition TM instance - backs up everything except the external.
2nd Partition TM instance - backs up first external to 2nd external.

Assuming the stuff on the external isn't changed much, there is very little risk in only backing it up every few days.

Are you suggesting changing the TM excluded files and target every few days? That sounds horrible.

pra9ab0y · Oct 24, 2009, 07:29 PM

Originally Posted by mduell

What?

Just the fact that if he/I wanted to take the 2nd drive somewhere or use it on a different computer he would have to use time machine to browse it. I personally wouldn't use it for the backup of an external drive.

besson3c · Oct 24, 2009, 07:36 PM

Originally Posted by ibook_steve

Exactly. I basically want Time Machine for my external drive, which does not have an OS on it. Just my stuff. However, if this is not possible, as it now sounds like, and RAID setup will wipe my original drive, it looks like I'm going to have to go manual.

Unless anybody has any other ideas.

Steve

You could buy the second drive, format it for RAID, manually copy all of your data to it, and then add the second drive. It should start "leveling" (i.e. mirroring) the data immediately.