USB Hard Drive Size Limit

Question

Level 1

9 points

USB Hard Drive Size Limit

Is there a TB size limit for external HDDs connected via USB on a mac?

I have both a 3 TB and 4TB external 3.5" drive that will not mount via USB. They are currently connecting via a hdd dock (with USB 3, FW, and ESATA ports) to a 2009 Mac Pro running latest version of Yosemite. They will however mount via esata, the internal sata drive bay and FireWire. Also, it seems that smaller sized HDDs ~1TB and under will mount (I haven't tried 2TB since I don't have one available, but I suspect it will work).

Note that this is not exclusive to the 2009 Mac Pro as I have tried it on the newest Mac Pro Cylinder and got the same results via USB 3. I found this was an issue in Mavericks too and tried Snow Leopard on an old iMac with the same result.

When I inspect the disk in disk utility via USB disk utility reads that the HDD is MBR when I know that it is GPT (GUID) and all the other connections read this correctly.

Any insight into this?

Thanks.

Mac Pro, OS X Yosemite (10.10), 2009 Mac Pro

Posted on Jan 1, 2015 9:46 AM

Reply

Answer 1

The hatter

Level 9

61,031 points

Jan 1, 2015 9:52 AM in response to giluta

How old is the dock? likely you need a newer model.

you should be able to check and see if they say anything about supporting drives larger than 2.2TB.

There is also a bug in Disk Utility with drives of 2.5TB and above that has been present since 10.8.3, in case you had the foresight to keep a clone of your 10.6.8 thru 10.8.2 systems.

And seeing how you did try on 10.6.8 already, the fault surely lies with the device and not the drive.

See what OWC http://www.macsales.com has to offer in a suitable replacement (then check Amazon perhaps).

Reply

Answer 2

giluta Author

Level 1

9 points

Jan 1, 2015 10:17 AM in response to The hatter

I don't think it is the dock. It works via FW and esata and it supports up to 4TB. On top of that, I have a LaCie external 3TB drive that has the same issue via USB 2 or 3 but works via FW. but I could be wrong

Reply

Answer 3

kahjot

Level 4

2,469 points

Jan 1, 2015 12:13 PM in response to The hatter

I have two external 3TB drives that connect OK via USB. One is a USB 3 drive hooked up to a 2010 Mac Pro (CalDigit USB3/eSATA card).

Reply

Answer 4

giluta Author

Level 1

9 points

Jan 1, 2015 12:47 PM in response to kahjot

Did you format the drives via usb?

Reply

Answer 5

The hatter

Level 9

61,031 points

Jan 1, 2015 1:17 PM in response to giluta

And LaCie in the past had to issue firmware update. There is a bridge, the means to interconnect SATA to USB and other interfaces.

Trial and error. Always fun. No other way except the vendor and chipset they use.

USB3 drive CASES should be okay.

Reply

Answer 6

kahjot

Level 4

2,469 points

Jan 1, 2015 10:31 PM in response to giluta

giluta wrote:

Did you format the drives via usb?

One of the drives is USB3 only, no other interface options, so definitely formatted hooked up to USB. The other one may have been formatted using FW. They were formatted using the Snow Leopard version of Disk Utility.

Reply

Answer 7

The hatter

Level 9

61,031 points

Jan 2, 2015 6:18 AM in response to kahjot

One of the drives is (connected via USB3... )

Drives are drives, and SATA. Know what you meant.

Some people have taken their internal drives, put in a USB device, formats properly, then return to use internally where the full capacity is seen and not an issue.

Why is DU treating internal drives on the SATA controller used an issue? really strange - and bad. But then Apple Pro RAID controller also limited drives to 2.2TB and would format as 800GB otherwise if they were larger.

Still points to the drive case.

And in using 3rd party PCIe USB3 controller, that could play a role as well.

Reply