OWC ThunderBay 4: Versatile Thunderbolt Enclosure

ThunderBay 4 Supports Hard Drives, SSDs, RAID, and Non-RAID in Any Combo

ThunderBay 4 extern 4 bay enclosure from Other World Computing.

 Courtesy of Other World Computing

OWC (Other World Computing) has long been a go-to place for Mac-related peripherals, so when the company started producing its own Thunderbolt-based external drive enclosures, my interest was piqued.

Thunderbolt has been part of the Mac's I/O capabilities since early 2011, and is now part of every current Mac model. Its big promise was to provide the fastest connection system between external devices and the Mac, but aside from Apple's own Thunderbolt display, and a handful of Thunderbolt external drives in various RAID configurations, there haven't been many Thunderbolt devices available.

Overview: OWC ThunderBay 4

The ThunderBay 4 is an external non-RAID Thunderbolt enclosure that can accept up to four standard desktop hard drives or four SSDs (adapter sold separately), or any combination of the two types of drives.

Because the enclosure doesn't include an internal hardware-based RAID, the Mac sees the drives installed in the enclosure as individual external drives, which allows you to decide how they will be configured. They can remain as individual drives, or you can use one of the available software-based RAID systems, such as Apple's Disk Utility or SoftRAID. We'll talk more about RAID capabilities a little later in this review.

The ThunderBay 4 comes in various configurations, including B.Y.O.D (Bring Your Own Drives) and with drives of various sizes pre-installed. All drives are 7200 RPM with cache size as noted. Current prices are:

Size Cache Configuration Price
B.Y.O.D N/A No drives $398.99
4 TB 128 MB 1 TB drive x 4 $649.99
8 TB 256 MB 2 TB drive x 4 $779.99
12 TB 256 MB 3 TB drive x 4 $879.99
16 TB 256 MB 4 TB drive x 4 $999.99
24 TB 512 MB 6 TB drive x 4 $1,399.99
32 TB 1024 MB 8 TB drive x 4 $1,799.99
40 TB 1024 MB 10 TB drive x 4 $2,279.99
48 TB 1024 MB 12 TB drive x 4 $2,949.99
ThunderBay 4 without Software RAID
Size Cache Configuration Price
B.Y.O.D N/A No drives $479.99
4 TB 128 MB 1 TB drive x 4 $749.99
8 TB 256 MB 2 TB drive x 4 $874.88
12 TB 256 MB 3 TB drive x 4 $979.99
16 TB 256 MB 4 TB drive x 4 $1,098.99
24 TB 512 MB 6 TB drive x 4 1,498.99
32 TB 1024 MB 8 TB drive x 4 $1,878.99
40 TB 1024 MB 10 TB drive x 4 $2,378.99
48 TB 1024 MB 12 TB drive x 4 $3,049.99
ThunderBay 4 with SoftRAID 5 pre-installed

ThunderBay 4 Hardware Overview

The ThunderBay 4 is small, especially when you consider what's housed in the external case: four 3½-inch drive bays, a 4-slot backplane, a Thunderbolt 2 (20 Gbps) to SATA 3 (6 Gbits/sec) interface, an internal power supply, and a cooling fan, all contained in an enclosure that measures 9.65 inches deep x 5.31 inches wide x 6.96 inches high.

Did I mention that the power supply is internal? That means no power bricks to kick around or lose.

The front of the enclosure contains a lockable panel that provides access to the four SATA drive slots. The front panel also includes five LEDs. The first indicates the status of power (on/off/standby); the remaining four provide access status for each of the four drive slots. The rear of the enclosure includes a Kensington security slot, dual Thunderbolt ports, an on/off rocker switch, an AC power cord connector, and a 3½-inch fan.

A word about the fan: The ThunderBay 4 needs a decent-size fan for adequate cooling of both the drives and the internal power supply. You can hear the fan, but it isn't overly loud. In an office environment, you probably won't even notice the fan noise, while in a quiet home or studio, you may hear the fan running. I prefer quiet equipment, but the fan noise was acceptable to me; your mileage may vary.

Drive Trays

The ThunderBay 4 uses drive trays (supplied) to house the drives. The drive trays are located behind the front panel. Unlock the front panel and swing the panel down and out to reveal the four drive trays. Each tray has a thumbscrew to secure the tray to a drive bay.

Drive trays are marked A, B. C, and D to correspond to a specific drive bay. This is for convenience only; you can swap the trays and drive bays at will, with no effect on the enclosure or drive performance.

Adding a drive to a drive tray is as simple as twiddling a screwdriver. Once installed in a drive tray, a drive can be used in any ThunderBay 4 enclosure. You can even buy spare drive trays, which would allow you to easily move drives between multiple enclosures, or store drives offsite.

2.5-inch to 3.4-inch drive brackets can be used to adapt the ThunderBay 4 for use with 2.5-inch SATA SSDs. The adapter is sold separately. 

ThunderBay 4 Testing and Performance

Our ThundayBay 4 test unit came configured with four 3 TB Toshiba DT01ACA300 7200 RPM hard drives. I connected the ThunderBay 4 to our test system, which consists of a 2011 MacBook Pro with 4 GB RAM, 2 GHz Intel Quad-Core i7, and a 500 GB internal hard drive.

I connected the ThunderBay 4 and MacBook Pro with the Thunderbolt cable supplied with the enclosure.

The ThunderBay 4 and its four drives were recognized at startup, and I set about using Disk Utility to format each as Mac OS Extended (Journaled).

With the formatting complete, I used BlackMagic Design Disk Speed Test, as well as Prosoft Engineering's Drive Genius 3, to measure the basic write and read performance of each drive in the enclosure. This was not an extensive test; what I was interested in was seeing if the ThunderBay 4 enclosure had any preferences in the performance of a drive bay. After benchmarking each drive, I powered down the enclosure and moved each drive down to the next drive bay. I then re-ran the benchmarks to see if there was any significant change in the benchmarks.

I learned two things from this test. First, that shuffling the drives from drive bay to drive bay is a piece of cake; they slide in and out with little effort. The second bit of information I learned is that each drive bay performs as well as any other; there were no sweet slots in the enclosure to worry about or take advantage of in testing.

Individual Drive Performance

I measured each drive's performance in the ThunderBay 4 enclosure. Average drive Read performance came in at 188.375 MB/s, while Write performance was 182.025 MB/s. Those are pretty impressive for the individual drives, but since I was just testing one drive at a time, I wasn't putting any kind of strain on the enclosure. I decided to see how well the ThunderBay 4 performs with various RAID arrays that use more than one drive at a time.

RAID Performance

Using Disk Utility, I created a RAID 0 (striped) array of two, then three, then all four drives, and measured each array's performance.

2 drive 3 drive 4 drive
Read 380.60 554.50 674.00
Write 365.50 541.30 642.60
Disk Utility RAID 0 (Stripe) MB/s - Disk Speed Test

Because I also wanted to test the ThunderBay 4 enclosure with SoftRAID, which provides a few more features than Disk Utility, including quite a few more RAID options, I decided to create the same basic RAID 0 arrays.

2 drive 3 drive 4 drive
Read 381.70 532.80 678.40
Write 350.20 535.90 632.00
SoftRAID RAID 0 (Stripe) MB/s - Disk Speed Test

Update: I ran an additional benchmark, QuickBench 4.0.4, to look specifically at the four-drive RAID 0 performance, which seemed a bit low to me with Disk Speed Test. I configured QuickBench to produce a custom test equivalent to what Disk Speed Test uses.

Disk Utility SoftRAID
Average Read 742.90 741.25
Average Write 693.17 646.89
4-Drive RAID 0 MB/s - QuickBench 4.0.4

While the MB/s numbers are slightly different in each of the two software-based RAID systems, the overall performance remained about the same; that is to say, neither provided any benefit at creating striped arrays. The important thing to note is that the ThunderBay 4 enclosure doesn't appear to be impacting performance, even when four bays are used concurrently. SoftRAID provides an added benefit in its ability to monitor the RAID arrays, detect possible failure modes, and send status updates to you via email, and even perform repairs with certain types of RAID arrays.

The next set of tests looked at using ThunderBay 4 and SoftRAID 5, which is available as an option with the enclosure. SoftRAID 5 offers some pretty amazing technology, including the ability to create additional RAID types, including RAID 1+0, RAID 4, and RAID 5. All three of these RAID levels offer the speed increase available from striping drives, with the benefit of fault correction, utilizing either on-the-fly calculated parity or a combination of striped plus mirrored arrays working in tandem.

Read 365.70 543.50 499.50
Write 324.60 380.20 375.70
SoftRAID 5 Advanced RAID levels MB/s - Disk Speed Test
Read 378.73 564.13 557.99
Write 318.64 496.02 500.25
SoftRAID 5 Advanced RAID levels MB/s - QuickBench 4.0.4

Note: All RAID configurations in this table made use of all four drives.

As you can see, there can be a performance penalty in using the RAID 1+0, RAID 4, or RAID 5 levels. But that penalty is easily offset by the added security of having parity (RAID 4 or 5), or having a mirror of the striped drives (RAID 1+0). I was actually pretty impressed by SoftRAID, and its ability to generate and process parity information without a huge hit on performance. In the not-so-distant past, this type of RAID would only be seen in hardware-based solutions because of the performance penalty software solutions incurred.


I'm very impressed by ThunderBay 4's overall design and performance. I like that OWC chose to leave the RAID options strictly in the user's hands. This allows the ThunderBay 4 enclosure to be used in many different scenarios: as a backup, as extra storage, or with various RAID configurations to increase performance. You could even use the ThunderBay 4 for multiple applications, say a two-striped RAID array for working with video, and a dual-drive Time Machine backup. The possible configurations are almost endless.

The SoftRAID app included with the ThunderBay 4 offers a number of capabilities beyond what's available in Apple's Disk Utility. If you're planning to use the enclosure in a RAID configuration of any type, I highly recommend SoftRAID. I've been using SoftRAID for years on our own server, to provide mirrored arrays with fault reporting and automatic rebuilding.

The ThunderBay 4 is an amazing product that can meet the needs of the professional who needs high-performance storage, as well as anyone who is looking for a versatile method of storage and backup. One size can indeed fit all.

Disclosure: Review samples were provided by the manufacturer. For more information, please see our Ethics Policy.