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eyadams · Mar 16, 2007, 09:23 AM

I have a lae 2004 G5. The original 160 GB drive is getting a little too full, so I bought a 400 GB drive to supplement it. I know I could move stuff over and around and manually manage files between the two, but I want something fancier.

Is it possible to set up some kind of RAID where the two physical volumes appear as one, even though they are different sizes?

If not, how do other people handle this kind of thing? Is there some way to move the /Applications and /Users hierarchies to the new drive, but leave the rest of the stuff on the old drive?

I guess I'm just looking for the least intrusive solution, so my less technical users (like my kids) won't have to worry about filling up the drives.

OreoCookie · Mar 16, 2007, 09:27 AM

Yes, that's possible, but if one drive fails, you'll practically lose all data, even if the files are located on the `good' drive.

BLAZE_MkIV · Mar 16, 2007, 10:47 AM

If you span them you'd loose all the data on a crash. Sounds like he's looking to just symlink a few directories ex: /Applications to /Volumes/NewDisk/Applications I remember some talk about doing this for /Users where all your data would be. Try searching (here and macoxshints.com) for move user directory.

pundit · Mar 16, 2007, 11:02 AM

Originally Posted by OreoCookie

Yes, that's possible, but if one drive fails, you'll practically lose all data, even if the files are located on the `good' drive.

Yep. He's trying to use a "JBOD" array, which isn't a genuine "RAID": it isn't redundant at all. It looks like the information you need to do so would be found in the Help for DiskUtility.

You should consider though that the failure rate for data on both drives increases (the first to fail will kill your "raid",) and a single new drive will have a lower mean chance of failure, than the combination you're suggesting. You should not that the most common form of disk failure is a disk head crash where the head physically makes contact with a disk platter, often causing the entire drive to be unusable (except through professional recovery.) Being a (and usually the only,) moving part, disks are the most vulnerable system component.

I've always liked a belt and braces approach to disks, and (software based) RAID 1 or disk mirroring is the minimal acceptable risk I'd have for data on my families computers, ensuring that the data will be much more likely to survive an "event."

This is a bit more expensive, but typically far less costly in a "life" sense than losing the stuff on your Mac.

eyadams · Mar 16, 2007, 11:42 PM

Thanks all for the comments.

I've decided to just move all my data to the new drive, and use the old one as a junk drive for non-essential stuff. Well, I'll be putting my music library on it, but since 99% of that is on CDs I know I've got copies and can afford to lose it. Though re-ripping them would be a pain.

Thanks again.

Moderator · Mar 17, 2007, 07:48 PM

just buy 2 x 250's, mirror them, and presto....instant auto catistrophic backup.

SSharon · Mar 18, 2007, 03:21 PM

Originally Posted by Moderator

just buy 2 x 250's, mirror them, and presto....instant auto catistrophic backup.

except if the file structure gets corrupted. A damaged file is still a damaged file even if you have two copies of it.

raid mirrors are for hardware failure only and should not be relied on for backup.
(I have mirrored 200gb boot drives in my MDD and use an external for backups).

eyadams · Mar 18, 2007, 07:44 PM

As implied by SSharon, backups are a separate issue. I have an external drive and I regularly backup the /Users hierarchy. For a while I would back up the entire disk, but that's no longer possible.

molarszbt18 · Mar 19, 2007, 01:00 AM

Why not use a program like Synk and every night sync the home folder on drive a to drive b...

CIA · Mar 22, 2007, 12:05 PM

Wow. teh suck.

cgc · Apr 5, 2007, 07:20 PM

I'm also looking into setting up a RAID 0 (Striped) on my MacPro using a couple of 250GB drives. I would have a 3rd 250GB drive in my computer for backups and would like the speed RAID 0 offers. With the failure rates of the current HDDs, I can't imagine RAID 0 is too bad so long as I backup.

mac128k-1984 · Apr 5, 2007, 09:30 PM

Originally Posted by cgc

I'm also looking into setting up a RAID 0 (Striped) on my MacPro using a couple of 250GB drives. I would have a 3rd 250GB drive in my computer for backups and would like the speed RAID 0 offers. With the failure rates of the current HDDs, I can't imagine RAID 0 is too bad so long as I backup.

I ran my Macpro for a while using a raid 0 setup. I eventually split it up, for a number of reasons.
First, was the data integrity, your right about failure rates, but the risk is still there, if the HD burps you could lose your entire drive. What I did to help mitigate that issue was running nightly backups to a third hard drive and monthly backup up to an external drive. Still the risk was there and I didn't feel like playing Russian roulette.

The next reason was firmware updates. While apple doesn't release them too often they do come out and the last two firmware updates would not work on a raid setup. That is you needed to boot the system up from a non-raided drive.

Third was bootcamp. I had a heck of a time installing vista on bootcamp. First you can only install bootcamp on a non-raided boot drive, even when I had that (I added a fourth drive that was loaded with osx (helped me with the firmware issue too) Vista just wouldn't accept the drive partition I created for it. Once I got rid of the the raid, reloaded OSX and bootcamp, vista installed problem and pain free.

All of those issues combined made it a real hassle for me to use a raid 0 setup. I'm sure a lot of people are happy with it, but for me, the risks and headaches were not worth the incremental speed bump

cgc · Apr 5, 2007, 09:58 PM

Thanks for the info mac128k-1984. I had researched 10,000+ rpm drives and there were none larger than 160GB. No real good option short of RAID 5 or 6 but I don't know if OS X can handle that and even if it does I have the issue of firmware updates. Grrr...would a seperate RAID card help? Not a big deal.

mac128k-1984 · Apr 6, 2007, 06:50 AM

A separate would help but the problem is if you plan to use it for the internal base. You have some work ahead of you. The drives snap into a back plane and not directly to the motherboard by a cable. I've with a fair amount of work, some people were able to get it done. Others I've read opted for an external raid array. That makes more sense for a lot of people who need a Raid 5+1 or Raid 10 configuration. Apple does indeed does support raid 5+1 but being a software solution you will incur a small performance penalty associated to mirroring the drives.