I just bought a LaCie 200GB drive. I want to split it up to mirror both sides. So when I add a file to 1 of 100GB partition it automatically adds it to the other partition. I want to do this incase I lose part of the drive.
In Disk utility partition the drive into two equal size partitions. Then drag them into the RAID section of Disk Utility and select the type of RAID you want. In your case RAID 1.
Using the same disk for RAID 1 is useless. Its very rare for a single partition on the same disk to fail in such a way that you NEED RAID. If one partition fails, then a diskutility can repair it in many cases.
I have only tried this same set up with two physical hard drives, so there is a chance OS X does not permit you the ability to use partitions in this manner.
Using the same disk for RAID 1 is useless. Its very rare for a single partition on the same disk to fail in such a way that you NEED RAID. If one partition fails, then a diskutility can repair it in many cases.
Absolutely correct. I work for a storage company. This is pretty close to useless. You're basically wasting half your disk for almost zero extra protection. All of the common failure modes will take down the entire disk. Buy a second drive-- you will probably need the extra storage at some point anyway.