December 08, 2011, 10:20 AM — The Macworld Lab has a small collection of Thunderbolt peripherals, and we thought we should put them to work to answer questions we had about connectivity and how devices affect performance.
After testing dozens of scenarios, we found that—for the most part—the two available bi-directional 10Gbps channels in the MacBook Pro (Late 2011) were more than able to keep up with the demand of multiple storage devices on a Thunderbolt daisy chain. However, if you add multiple displays to that chain, the throughput of some drives can be severely limited.
(For your reference: The iMac (Mid 2011) uses the same Light Ridge Thunderbolt controller as the MacBook Pro, but the iMac has two Thunderbolt ports and offers up to four bi-directional, 10Gbps channels. The MacBook Air (Mid 2011) uses an Eagle Peak Thunderbolt controller that allows for two bi-directional 10Gbps channels.)
Drives in a daisy chain
The Thunderbolt drives involved in our testing were the Promise Pegasus R6 RAID array, the LaCie Little Big Disk Thunderbolt Series SSD, and the LaCie Little Big Disk Thunderbolt Series 2TB hard drive.
To get a set of baseline speeds to gauge performance, we attached one drive at a time, with no other devices, to a 17-inch 2.4GHz Core i7 MacBook Pro. We ran the AJA System Test several times—specifically, the 2GB, 1920-by-1080, 10-bit RGB test—and calculated average performance speeds. The Pegasus R6 was the fastest device we tested, with a write speed of 538.1MBps and a read speed of 519.3MBps. The LaCie SSD posted a write speed of 253.0MBps and a read speed of 480.5MBps. The LaCie hard drive clocked in with a write speed of 184.7MBps and a read speed of 203.1MBps.