3TB internal hard disks on the Mac Pro and 3TB drives on the Apple RAID

We’ve been experimenting with the Seagate Barracuda XT 3000GB on various Macintosh configurations. In the past one could take out, for example, four 500 GB drives and replace them with four 1TB, 1.5TB, or 2TB internal drives.

The result for four 2TB drives configured in RAID 5 is a drive that is about 5.23TB with redundancy.

With the release of 3TB internal hard drives, such as the Seagate Barracuda XT above, many Windows PCs can’t make use of more than approximately 2.2TB due to the use of MBR (see 1, 2). Apple on the other hand, has been using the GUID partition table (GPT) for some time (since 10.4.0 in early 2005) so the Mac OS X should be able to make use of larger than 2.2 TB hard drives.

In some respects the tests so far demonstrate this. The results so far:
1. On a 2008 Mac Pro (MacPro3,1 Quad-Core Intel Xeon, 3 GHz, 2 processors, 8 cores) with RAID Card (1.00, M-, the drives only show up as 2.2 TB.
2. On a 2008 Mac Pro (MacPro3,1) without the RAID Card, the drives show up as 3.0 TB.
3. On a 2010 Mac Pro (MacPro5,1) with RAID Card (2.00, E-, 0018) the drives show up as 2.2 TB.
4. On a 2010 Mac Pro (MacPro5,1) without the RAID Card, the drives show up as a full 3.0 TB.

In short, Mac OS X appears to have no difficultly using hard disks that are larger than 2.2TB, except when those drives are connected to an Apple RAID Card.  Apple does warn “Do not assume that the block size is always going to be 512 bytes” and does not support SSD with the current RAID card.  Apple states that “Solid-state drives are not compatible with the Mac Pro RAID Card in either RAID or Enhanced JBOD mode.”  My hypothesis as of now is that Apple did not heed their own warnings on block sizes on the Apple RAID card which is why hard drives attached to the RAID Card seem to be limited to 2.2TB.

Some performance notes on the 3TB Seagate Barracuda’s will follow shortly.

6 thoughts on “3TB internal hard disks on the Mac Pro and 3TB drives on the Apple RAID”

  1. Chris, do you think that Apple could apply a firmware update to the Apple Raid card in order to support the new 3TB drives, or does one have to start thinking about purchasing an alternative?

    I can confirm that you do indeed see 3TB posted above even with an internal eSATA card connected to NewTech external drive holder. I did not test the 3TB drive with the Apple Raid card however, but it does sound like 3TB is not supported yet according to what I’ve read on other sites as well.


    1. I don’t know enough about the card to say whether a firmware update would help. It would be nice if it did, but I don’t know. I just hope Apple either releases a firmware update or releases a new card that supports larger than 2.2TB per drive. 😉

  2. Just seeing if there has been any headway on this? Firmware update? What would be the downsides to installing a 3rd party raid controller that supports 3tb drives?

    1. As far as I am aware, there were no firmware updates. Likewise, it looks like on the Apple Store that the current minor Mac Pro update doesn’t even have a RAID option available (at least that I can find today). So, I think the best option would be a 3rd party card if you want to go internal.

      I ended up just using one of the Mercury Elite Pro externals. Seems to be reliable.

  3. Apple did (temporarily, hopefully) remove the Apple RAID Card as a build-to-order option on the Mac Pro, but it’s still avaialble as a separate item that you install yourself (which is simple).

    Hopefully they’ll have a firmware update (or a new version of the card, if nothing else) that accomodates today’s larger drives.

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