What happens if I pull out one drive of a raid set?

If you pull it, everything will operate as normal, yes.

When you replace the drive, you will first have to go into RAID Admin and mark the drive as available for use (because it knows the drive used to be in working order, but the RAID has no idea why the drive unmounted). Once you do this, the RAID will immediately begin rebuilding the mirror.

Well, if you post in a forum dedicated to the product called Xserve RAID, then forgive me if I give advice related to that product 😉

You can't use RAID Admin for stuff in the Mac Pro. You need to use Disk Utility. I actually don't recall whether the sync is automatic or manual with OS X -- I suspect manual -- you probably need to something in Disk Utility to specify it should rebuild the mirror.

You'd probably have better luck checking the Mac OS X forum or the Mac Pro forum (the OS X forum is the "right" place as this is a software question) -- I'm sure this has come up over there pretty frequently.

Why are you planning/expecting to do this?

The only thing that comes to mind is that you're trying to use the mirror as a backup drive of some kind. If that's the case, don't do this. It will probably work, but there are far better, more reliable ways of doing this.

For example, get an external FireWire drive and backup to that, either using Disk Utility to periodically clone your internal drive, or any number of free and/or commercial applications. By the time Leopard comes along you can use Time Machine to keep a (close to) real-time backup of your system on the external drive. If you want to store the backup off site you can do so, and any time you plug it back in the OS will synchronize any changes.

Breaking a mirror is a bad way of managing backups.

Fortunately by today's standards 380GB is not all that big.
As Camelot says, breaking a not a good way to go.
You are also right that the Finder is not the best tool for this job. It should be able to copy the whole 380GB without issue- but it will have to take the whole lot.
Retrospect would be a better choice.
Retrospect can work in two ways
- It can copy all of the files over the first time, then subsequently only copy the files which have changed. It can also delete the files which have been deleted from the source disk. Then each day you will have a copy of your source, but not way to get back to yesterday or the day before. The files are stored in folders just like on the source.
- It can run a backup and store all of the files in a Retrospect file. Each day you run an incremental and it writes the changed files into the Retrospect file and keeps track of changes. You will need retrospect to recover the files, but you will also be able to recover files from yesterday (and as far back as your first backup run.

If your data set starts at 360GB, how much data actually changes each day? If you use a 500GB FW drive then you might be able to do a week on one drive. Get two and rotate them each week.
And leave the drive in the car. If you have a fire during the day and the backup drive is plugged into the server then your whole plan is for not.

Reese

I used Retrospect quite a bit on OS9, great app. It's a shame when a great product gets bought and ship wrecked.
If you just want to sync the drive then it can be as easy as a line line script calling rsync, or there are a few apps out there.
If you want versions then, as Camelot said, you can wait for Time Machine in Leopard which should be out "this spring", or you can purchase another backup utility like BakBone or BRU (from Tolis Group).

You mentioned that you work for a News Paper. On 12/3 the SF Chronicle ran a big article titled "Google- The Lost Tapes". The article was a bit of a disappointment, but the punch line was that the tapes were 'lost' because a dispute among the the editorial staff resulted in a hard disk scrub party as some folks headed for the door.
Clearly that news paper did not have a working disaster recovery program in place. I would also suggest that you contact a professional in data retention and build a real disaster recovery program. If you have data you will loose data. Not a matter of if, but when.
Good luck.

Reese

Check out Deja Vu. Seems to work fine in 10.x.