Apple OS X Forum
Thunderbolt - read/write issue
Thunderbolt - read/write issue
by John Kotarski on Oct 29, 2013 at 11:27:27 pm

I am running Mac OSX 10.7.5 and have a problem with read/write permission when I connect a Seagate external hard drive (Backup Plus 1Tb and Backup Plus 3Tb) via Thunderbolt. I can read/write the drives when connecting via USB 3.0, but when I connect using the Seagate Thunderbolt adapter, I can only read the drive but not write to it. Disk utility will not highlight verify permissions for either of the drives. Any ideas?

Re: Thunderbolt - read/write issue
by John Kotarski on Oct 30, 2013 at 9:47:25 pm

Here is a fix that worked for me:

The drives need to be formatted as ‘Mac OS Extended (journaled)’ and the partition map scheme is ‘GUID Partition table’.

This can easily be done using the ‘Disk Utility’ accessible from the finder. Once in Disk Utility, select the drive and then select the partition tab. From there, select ‘1 partition’ and under options ‘GUID Partition table’, then ‘Mac OS Extended (journaled)’. After this is complete close window. Select the drive icon and right click to get info. It should show your permission to read/write the drive.