I am struggling with this and am wondering if anyone could help. I currently am using a imac running osx snow leopard with a windows 7 partition. I have two WD 500 firewire HD's daisy chained together. Initially I had the main drive partitioned in half, 1 in mac journal for my time machine backup, the other in fat so I can backup data that could be recognized and written to by my windows partition.

I have been trying to raid these drives together so they mirror each other. What I have been struggling with is once I create the raid the partition gets deleted and the raid become either mac journaled or fat, not both. I assume I am doing something wrong.

Basically I am trying to have both 500 gig drives mirrored and at the same time have a mac journal and fat partition.

I know there is software I can buy so my windows side can read and write to mac journal, but in case I want to bring the drive to a pc outside of my setup I want the ability to have a fat partition.

11/6/2009 11:30:29 PM

if you're mirroring the drives, you're going to have 500gb of effective free space.

once you have the software raid array set up, you can partition the actual array (not the drives themselves) any way you want (e.g. 250GB HFS+ and 250GB FAT32). it'll show up in disk utility just like any other disk.

also, i'd recommend that you download macfuse and use NTFS-3G instead of FAT.

11/7/2009 12:01:45 AM

Right you are doing it backward. RAID first, then partition. The RAID set becomes a single logical disk which can be treated (for the most part) like a single physical disk, including partitioning with multiple file systems.

Thanks for the macfuse tip evan, didn't know it existed. That looks totally awesome. Basically a mini VMWare for file systems.

11/7/2009 8:18:22 AM

fyi, be careful about Mac RAIDs with USB drives. Don't be surprised if the RAID continuously fails and reports bad or damaged drives, when in fact there's nothing wrong with the drives.

here's a discussion I had when I was having problems with my new 2x 1TB RAID last month
http://discussions.apple.com/thread.jspa?threadID=2190025&tstart=0
I ended up just killing the RAID and using the 2nd drive as a Time Machine to back up the 1st drive.
If you already have a time machine drive, though, not sure that would help

11/7/2009 2:26:46 PM

Evan thanks for the help. I am still struggling with partitioning after I raid the drives. When I choose the raid option in disk utlity I then click the Plus button and then drag each drive to it. When I click create it creates the raid as what ever format I choose, i.e. mac journaled. When the raid is created and is visible in disk utility there is not a partition option under the raid drive, and each drive does not allow me to partition it. What am I doing wrong? I can post screen shots if that would help.

Again thanks for all the help.

11/8/2009 12:10:09 AM

ah, you're right. there indeed is not a partitioning tab.

from a quick google search, it doesn't look like the native software RAID stuff will let you have multiple partitions. you could try messing with diskutil to see if you can do it manually... but i wouldn't get your hopes up.

sorry to mislead you - i wasn't near my mac at the time, and apparently my memory fails me.

i think your best option is to do what agentlion suggested and use the second drive as a time machine drive.

11/8/2009 3:11:18 AM

Also thank you for the tip on macfuse. The big reason I wanted to do this is because my first external was making weird noises and I wanted to make sure my stuff was safe. It is still kicking so I am going to take agentlion's advice and use my new drive to be primary time machine backup and old drive as extra storage.

On the topic of formatting in ntfs-3g would the only real benefit gained be the ability to save larger files compared to a fat formatted drive? Or are there other large gains formatting in ntfs-3g?

11/8/2009 7:38:11 PM

http://ixbtlabs.com/articles/ntfs/index3.html

11/8/2009 8:23:23 PM