Introduction
The NewerTech/Other World Computing miniStack is one of several external drive enclosures now available that are designed to sit under the Mac Mini and to match its footprint and design. Along with a 3.5-inch, 7200 RPM hard drive (in sizes from 80 GB to 500 GB) the miniStack includes three FireWire 400 ports, three USB 2.0 downstream ports, and one USB 2.0 upstream port. It also includes a two-speed, temperature-controlled fan and an auto-power feature that turns it on and off as the Mini is turned on and off.

In addition to performance, we were curious about three things going into the review:
Heat: With the miniStack positioned directly under the Mini, would the heat from the 3.5" hard drive cause the Mini to run too hot?
Noise: Although the Mini does have a fan, it's very quiet in operation, even in a room with no other computers or noisemakers. Would the miniStack's fan preserve that quiet?
Fit and finish: The Mini is a good-looking box in its understated way. Would the miniStack live up to that standard and really look like it fit in, or would it look like tennis shoes under a tuxedo?

Review System

The miniStack we received had a 160GB, 7200-RPM Hitachi Deskstar drive with an 8MB cache. We tested it with a 1.42GHz Mac Mini running Mac OS X 10.4.2 with 1 GB of RAM and the standard 80GB, 4200-RPM internal drive.

Fit and Finish
The miniStack is a good-looking unit, 2/3 of the height of the Mini itself and with the same aluminum-colored sides and white top. The sides of the miniStack are plastic rather than aluminum, and the color on our unit was slightly darker than the Mini, but neither was noticeable without a close look. The layout of the back panel is a bit tight (at least if you're blindly trying to plug in a cable from the front), but it's about as good as it can be, given the number of ports, plugs, and switches occupying the space.

The white top of the miniStack can be removed much the same way the Mini's top is removed (and using the same tool). The insides reveal a clean and simple layout that's less cramped than you might imagine (especially after looking inside the Mini).

The one oddity is the orientation of the large aluminum heat sink that wraps around three sides of the hard drive. The fins on the heat sink project downward, through a rectangular hole in the bottom of the case. Clearly it wouldn't be a good idea to have the fins project upward through the top of the case, venting heat directly up into the Mini, but we do wonder about the efficacy of trying to radiate heat downward, especially given the slim air space under the miniStack. As noted below, however, heat buildup was not a problem on our test unit.

In all, the miniStack looks to be a well-built unit.

Setup
There's not much to set up: Unbox the miniStack, slide it under the Mini, plug in the power cord, connect the FireWire and USB ports to the Mini, and turn it on. The top of the miniStack has a slightly raised edge all around that helps the Mini sit securely in place, and the package includes short (7") FireWire and USB 2.0 cables to help keep down the cable snarl.

There are only two options in the setup: The fan can be set to High, Low, or Automatic; we left it on Automatic, the factory default. The ports also have an option switch that lets you choose between FireWire, which will cause the miniStack to connect to the Mini using the FireWire port, and Automatic, which will use either the FireWire or USB 2.0 port, sensing which is connected to the Mini. A four-page installation guide (the only documentation included) recommends setting the switch to FireWire rather than Automatic if using a FireWire connection (though it doesn't say why that's preferred).

Operation
The day-to-day operation of the miniStack was trouble-free during our test period.

The extra FireWire and USB ports are a plus for connecting scanners, printers, card readers, and such all at once. We wish, though, that at least one FireWire and one USB port were on the front of the unit to provide easy access for temporary connections. (A look inside shows that such a change would not be dead simple. The circuit board and fan would have to be narrower to make enough room in the front for the ports.)

As it was, we managed to accidentally disconnect the Mac Mini's none-too-secure power connection a couple of times when pulling the stacked units forward to plug or unplug cables. The power cord connection is definitely not one of the Mac Mini's best features.

The miniStack has a blue light on the front that serves as a power light and also flashes during disk access (something we miss on the Mini itself). The auto-power off and on function worked well, with one minor surprise: When the Mini shuts down, the blue power light on the miniStack stays on (because its power switch is still on) and its fan may continue to run for a few minutes to cool down the drive. At first that made it seem as though the auto shutoff had failed to work, but a few minutes' patience showed that it had.

To monitor the Mini's temperature, we used Marcel Bresink's free Temperature Monitor Lite. The Mini appears to have only one temperature sensor, the SMART sensor for the hard drive, so there's no way to tell what the more important CPU temperature is. However, using the hard drive temperature as a relative measure, we found that having the miniStack underneath the Mac Mini raised the Mini's recorded temperature by 5 to 7 degrees Fahrenheit under load. In all, the extra heat did not seem to be a concern, as the Mini generally runs fairly cool to start with.

The miniStack's two-speed fan was louder than the Mini's own fan, particularly at the higher speed. It was clearly audible in our quiet test room (as was the Mini's fan) but would probably not be noticeable in a room with other computer fans or similar background noise.

We were able to use the miniStack as the startup drive as well as a second drive and, in fact, used it as the startup through most of our test period. The only drawback to this setup is that when using the auto power on function, the miniStack drive doesn't spin up quickly enough after a shutdown, causing the Mini to boot from its internal drive instead. This delay is not a problem if the miniStack is used as a secondary drive, of course, nor is it a problem if you sleep the Mini at night rather than shutting it down.

Performance
The 5400RPM internal drive that came with the Mini tested in our original Mac Mini review provided adequate performance. The internal drive in our newer Mini (used for this test), however, was an 80GB, 4200RPM unit that was causing regular appearances of the rainbow wait cursor, as the OS and various applications accessed the disk. So we were more than a little interested to see whether the miniStack, with its fast 7200RPM drive, would make a difference, especially when used as a startup drive.

The benchmark results below tell the full story, but the short version is that the miniStack provided a noticeable kick in everyday use. Despite the limitations of a FireWire 400 connection, the miniStack showed roughly double the performance of the slow internal drive, and spinning rainbows all but disappeared.

File Duplication Time
One of our standard "real-world" tests of disk performance is to duplicate a large folder in the Finder. The folder contains ten copies of a 20.7-MByte file, for a folder size of 207.5 MBytes. In this case, we tested the internal Mac Mini drive when set as the startup drive, and the external miniStack drive when set as the startup drive. We ran five trials on each disk, discarded the worst result from each set, and averaged the remaining four. (Spotlight indexing was disabled during all tests.)

We also list the result from our hot-rodded Mac Mini 1.25GHz system, in which we installed a $230, 7200RPM, 60GB Hitachi 2.5-inch drive internally (not a job for anyone but an accomplished computer technician with excellent documentation at hand). And we've added results for a Fujitsu 5400RPM 80GB drive Apple shipped in a PowerBook G4/1.67GHz.

Finder File Copy
Time (sec.)

Mini internal drive
26.5

miniStack drive
14.6

Hitachi 7200RPM internal
13.8

PowerBook G4 internal
20.8

Xbench Disk Performance Rate

We also ran the Disk Test portion of the Xbench benchmarking program (Version 1.1.3). (Actually we ran the whole suite of Xbench tests, but as expected, the only variation was in the Disk Test results.) As with the file duplication test, we ran five trials on each disk, discarded the worst result from each set, and averaged the remaining four.

Xbench Performance
Mini internal
miniStack
PowerBook G4

Overall Disk Score
44
104
76

Sequential Access
44
96
92

Uncached Write
[4K blocks]
38
108
87

Uncached Write
[256K blocks]
51
83
81

Uncached Read
[4K blocks]
37
103
131

Uncached Read
[256K blocks]
55
95
83

Random Access
44
114
72

Uncached Write
[4K blocks]
30
139
78

Uncached Write
[256K blocks]
43
123
66

Uncached Read
[4K blocks]
65
104
68

Uncached Read
[256K blocks]
55
99
77

Conclusions
With its combination of fast hard drive, extra FireWire and USB ports, space-saving form factor, and Mini-matching looks, the miniStack makes a solid add-on for the basic Mac Mini, particularly if your Mini happens to be lumbering along with a 4200RPM drive. Prices range from $99.95 for the enclosure without drive up to $499.99 for a 500GB configuration, which seems reasonable enough given the extra ports and form factor.

Several other manufacturers are marketing units with similar combinations of drives, ports, and looks, so it wouldn't hurt to shop around some. A few also offer hard-disk-only units, though we can't imagine why anyone would pass up the extra ports