The Western Digital My Passport Pro has two RAID options, each of which is useful: striped for speed, or mirrored for security. We took benchmarks for both configurations. The figures given below are the average results after five test runs.

Striped RAID 0

Blackmagic Disk Speed Test
5GB stress test
Write 204.68 MB/s
Read 204.94 MB/s

QuickBench
Small files (<1MB) average
Sequential read 162.257 MB/s
Sequential write 142.61 MB/s
Random read 19.16 MB/s
Random write 41.09 MB/s

Finder
2.5GB file transfer
22 seconds

Mirrored RAID 1

Blackmagic Disk Speed Test
5GB stress test
Write 104.12 MB/s
Read 108.08 MB/s

QuickBench
Small files (<1MB) average
Sequential read 73.225 MB/s
Sequential write 77.877 MB/s
Random read 18.406 MB/s
Random write 25.713 MB/s

Finder
2.5GB file transfer
24 seconds

Our My Passport Pro sample came configured in the striped RAID 0 configuration, so that's what we started our tests with. We were impressed with the results.

Transfer speeds peaked at over 200 megabytes per second, which is superb for a portable drive, or at least one that isn't an SSD. The much lower speeds for random read/writes of small files are no surprise – it's not what hard drives are good at. But with the striped RAID 0 setting spreading the data across both drives and using as much Thunderbolt bandwidth as it can, you're looking at potentially double the data transfer speed compared to a single-drive device, such as the Freecom Mobile Drive Mg 1TB.

Blackmagic's test suite indicated that the drive should be suitable for professional, uncompressed video work up to 1080p (10-bit YUV 4:2:2, if you care about such things) and we had no problems using it as a primary drive when working.

Thunderbolt
The Thunderbolt standard is well utilised

It's true that you get better performance with SSD-based drives (typically around 300 MB/s, so a 50% increase – not insignificant) but not in anything close to this kind of price-per-gigabyte ratio. Even a single 1TB SSD will set you back as much as the 4TB version of this drive.

Set to mirrored RAID 1, it's no surprise that speeds drop to around half – you've gone from spreading the data over two drives to effectively just one, after all (technically, it's all going on the second drive since you're mirroring, but that doesn't help with the speeds).

You might have noticed that our 2.5GB single file transfer time was almost identical in both cases, though – a reminder that individual real-world situations don't always reflect what the benchmarks say.

RAID
The RAID configuration is up to you

Switching between the two RAID modes is easy using WD tools. These come loaded on the hard drive in DMG form. You can switch RAID modes, run SMART tests and erase the whole thing easily enough. There are no encryption tools as part of WD's suite, though.

In use, the drive is quiet at first, but once you start using its two drives intensely, the fan at the back kicks up a pretty notable whirr – it's high-pitched, and yes, somewhat intrusive. It'll stand out even in a busy office environment. It's understandable (the unit gets pretty warm even with the fan at full whine), but it means that if you're doing any kind of audio editing, you'd better have remembered your headphones.