I just installed new drives in my MacPro and cannot find the RAID option in Disk Utility

one reason to keep old clones around that you can use in a pinch, prior to 10.8.4 there was no issue with 3TB drives.

Dual boot - so you can continue to work with Mountain Lion while and until Mavericks is also been updated (I tend to find the last build the one to use and skip all the ones that came before)...

Not sure about the 1TB drive - by itself tells us nothing.

I had high hopes that once the known issue with drives larger than 2.2TB was reported and confirmed it would be gone; and, Mavericks touted all new RAID features and on the fly adding to an array much easier.

Dual SATA bare cases are cheap enough from OWC and others, somewhat noisy to my ear, will get you back up and running. Leave them as external? do you have USB3 or eSATA III/6G controllers to use?

I was able to work around this issue.

I have a 2010 MacPro running Mavericks 10.9.1.

I had read somewhere that before I RAID the drives it is best to Erase securely with zeros so the bad blocks can be identified. Sounds good. I did the secure erase (1 pass) -- took 5 hours. One note on this, I started one drive using the GUI Disk Utility application and then opened Terminal and started the other. The Disk Utility OSX GUI App only lets you do one at at time -- would have taken 10 hrs.

Let's name the two drives. "drive4" was zeroed with Disk Utility app. When zero was over it showed up in Disk Utility and I then did a quick non-zero format and it showed up on my dekstop as "drive4".

Let's name the other drive "drive3". This one I zeroed from the Terminal. When complete it showed up in Disk Utility GUI app only as main hard drive -- no sub label. I could not even do a quick erase again. I finally erased it from "diskutil" Terminal and it then showed up in Disk Utility GUI. From Disk Utility GUI I then did another quick non-zero (just regular) erase and now both drive4 and drive3 were showing on desktop.

At this point I then realized there was no RAID option. Read this thread and do not have an external Raid enclosure. I did an "eject" of both "drive4" and "drive3" from my desktop. From the Terminal I did a "diskutil list" to show the drives. Found the ones I needed and issued the "diskutil createRAID mirror raid0 JHFS+ disk1 disk2" command -- note here that the two drives were showing up as "disk1" and "disk2" under the "IDENTIFIER" column of the output for "diskutil list" command. This createRAID worked perfectly.

I then went to Disk Utility GUI app and the RAID look just like the RAID for the other two drives that I have in my MacPro. The RAID tab is now there and everything. No external drive enclosure needed.

If you open multiple windows in Disk Utility you can do concurrent operations.

Sometimes a restart is needed to get drives to show up.

Sounds like it is all working.

If you open multiple windows in Disk Utility you can do concurrent operations.

Thanks for that Tip!

I always assumed it was Single-Threaded!

I had the same problem in attempting to set-up a RAID 1 in a classic MacPro running OS 10.8.5, using 2 new Seagate 3TB drives as internal data drives 3 and 4 (not to boot the machine with) and encountered all the same problems described earlier here. The problem is clearly with Disk Utility in that version of the OS and knowing that, this was my workaround:

I attached a bootable USB external drive with OS 10.6.8 and restarted the MacPro from that disk. I then selected Disk Utilities and (re)erased the two target drives (Mac OS Extended (Journaled)). I then restarted with OS 10.8.5 where at the end of the boot-up I got a prompt saying the drives need to be updated to use with this version of the OS, but ignored that and the drives did not mount. I then launched Disk Utility where the drives appeared as expected and proceeded with setting-up the RAID normally with no other issues.

Hope this helps.

Thanks to your question and resolution I was able to correct the same issue on my Mac Pro.

This was the only solution that worked for me. After many hours of trying all the other suggestions, this did the trick. Also I might mention that this was the quickest of all the options I tried before.

Thanks Dave Turner3! You Rock!