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-126.96.36.199), 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-188.8.131.52, 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.