Western Digital (WD) today released a portable external drive for Macs and a dual-disk external desktop backup drive that it claims is faster than a solid-state drive (SSD).

WD announced the My Book VelociRaptor Duo desktop backup drive and the My Passport for Mac. The My Passport for Mac portable drive comes with one 5Gbps USB 3.0 port.

On the performance side, WD is touting its VelociRaptor Duo as king of the heap. The performance of the VelociRaptor Duo is at least as good as any consumer SSD, even though it contains hard drives, according to Ralf San Jose, WD's new branded product manager. "However, you get eight times the capacity of [the average] SSD."

This past spring, WD released 4TB and 6TB My Book Thunderbolt Duo external drives. Those desktop backup drives, however, used slower 7,200rpm WD Caviar Green internal hard drives.

The new My Book VelociRaptor Duo comes with two 10Gbps Thunderbolt ports and uses the RAIDed capacity of two 10,000rpm VelociRaptor internal hard drives.

One notable feature of the desktop VelociRaptor Duo is it comes with a Thunderbolt cable, which can typically cost up to $49.99. But the VelociRaptor Duo isn't cheap at $899.

Still, San Jose pointed out that in a price-per-gigabyte comparison, the VelociRaptor Duo comes in at 43 cents per gigabyte, while most SSDs cost anywhere from $2 to $3 per gigabyte.

In reality, some lower-capacity SSDs have fallen below $1 per gigabyte. However, the VelociRaptor Duo does more than halve the price of capacity compared with a larger SSD, and 1TB SSDs are far and few between; the ones that are available, such as OCZ's Octane, cost more than $2,400.

The My Book VelociRaptor Duo has a maximum performance of 400MB/sec for reads and 380MB/sec for writes, but because of its Thunderbolt ports, it can be daisy-chained with additional external drives to increase its performance.

WD's My Book VelociRaptor Drive daisy-chained to other hard drives using the Thunderbolt port specification

"You can daisy chain two VelociRaptor Duos together, giving you 800MB/sec for reads and 760MB/sec for writes," San Jose said. "We haven't seen performance like this in the hard drive industry pretty much until now."

By comparison, the 1TB OCZ Octane SSD sports a top speed of 460MB/sec for data reads and 330MB/sec for writes. WD's own My Book Thunderbolt Duo, which uses the two Caviar Green internal drives, has read/write speeds of 244MB/sec and 235MB/sec, respectively.

According to San Jose, using the Thunderbolt ports, the VelociRaptor Duo can transfer 2,000 5MB .mp3 files in 9 seconds, a 22GB HD movie in 65 seconds and a 5GB SD movie in 16 seconds.