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The drives
Apart from Seagate's new Momentus 5400.3, which is the first 2.5" drive to use perpendicular recording technology, mobile drives from competing manufacturers are quite similar to one another. Unfortunately, the Momentus 5400.3 is ATA-only, so it can't play in this Serial ATA roundup. Look for more in-depth coverage of that drive around here soon.

Since 2.5" Serial ATA drives don't differ much in terms of features and form factor, we have to bust out the spec sheets to see how they compare on paper. We've compiled the essential specs for Seagate's Momentus 5400.2 and 7200.1 models, as well as Hitachi's Travelstar 5K100 and 7K100 families, below. Most of the specs line up, making comparisons easy. However, hard drive manufacturers don't always make the same information available.

  Momentus 7200.1 Momentus 5400.2 Travelstar 7K100 Travelstar 5K100
Maximum external transfer rate150MB/s150MB/s150MB/s150MB/s
Average sustained transfer rate45.8MB/s42MB/sNANA
Media transfer rateNANA78.6MB/s (100GB)
70.1MB/s (80GB, 60GB)
Read seek timeNANA10ms12ms
Write seek timeNANA11ms14ms
Average seek time10.5ms12.5msNA12ms
Average rotational latency4.2ms5.6ms4.2ms5.5ms
Spindle speed7,200RPM5,400RPM7,200RPM5,400RPM
Available capacities100GB, 80GB, 60GB120GB, 100GB, 80GB, 60GB, 40GB, 30GB100GB, 80GB, 60GB100GB, 80GB, 60GB, 40GB
Cache size8MB8MB8MB8MB
Platter size50GB (100GB)
40GB (80GB)
30GB (60GB)
60GB (120GB, 60GB, 30GB)
50GB (100GB)
40GB (80GB, 40GB)
50GB (100GB)
40GB (80GB, 60GB)
50GB (100GB)
40GB (80GB, 60GB, 40GB)
Idle acoustics2.5 bels2.4 bels2.6 bels2.5 bels
Seek acoustics2.9 bels2.9 bels3.0 bels2.7 bels
Standby power consumption0.28W0.28W0.25W0.4W
Idle power consumption0.95W0.8W0.9W0.85W
Seek power consumption2.6W2.2W2.7W2.5W
Read/write power consumption2.4W1.9/2.3W2.3W2.0W
Native Command Queuing?YesYesYesYes
Warranty length5 years5 years3 years3 years
Price (street)(100GB)(120GB)(100GB)(80GB)

2.5" mobile drives don't yet support 300MB/s Serial ATA transfer rates, so all the drives we'll be looking at today top out at 150MB/s. The faster Serial ATA interface really only benefits burst transfers, so the fact that it's missing shouldn't be a big concern.

Unfortunately, Hitachi and Seagate disagree on how to communicate the internal transfer rates of their mobile drives. Seagate prefers to give the average sustained transfer rate, which is measured at the middle of the disk. Hitachi's data sheets, on the other hand, give the media transfer rate. This is the transfer rate for the highest density, furthest outer-diameter zone, so it's more of a best-case scenario. Obviously, it's impossible to compare the Momentus drives' average sustained transfer rates to the Travelstars' media transfer rates, but the numbers are useful for comparing 5,400 and 7,200-RPM drives from each manufacturer.

Reporting spindle speeds is something both Hitachi and Seagate can agree on, but seek times are another story. Seagate gives the seek times for its Momentus drives as an average, but Hitachi breaks the seek time down into read and write components. Oddly, though, Hitachi quotes an average seek time for its Travelstar 5K100 but not for the 7K100. Regardless of how they're reported, seek times look pretty consistent between the Hitachi and Seagate drives. The 5,400-RPM drives obviously have much slower seek times due to their slower spindle speeds, and that will invariably impact performance.

Platter size can also have an impact on performance, as platters with higher areal densities allow more data to be accessed over a shorter physical distance. Seagate can claim a density advantage here, as it's the only one with 60GB platters. Those platters are only available on the Momentus 5400.2, though, and then only on certain models. The platter size for 7,200-RPM drives from both manufacturers tops out at 50GB, although again, it depends on the total capacity of the drive.

Moving to acoustics, there's actually little difference between the idle and seek noise levels quoted by Hitachi and Seagate. We'll be doing our own noise level tests to see which drives prove quieter in the real world. Power consumption will be tested, as well, although based on the drive specs, it's likely there will be little difference between the drives.

Speaking of little difference, all four drives we'll be looking at today support Native Command Queuing and have 8MB of cache. Warranty coverage differs between the two manufacturers, though. Like all Seagate drives, the Momentus 5400.2 and 7200.1 are covered by a five-year warranty, while the Hitachi drives are only covered for three years. That's a pretty significant difference, but it's important to note that longer warranty coverage doesn't necessarily mean that Seagate's drives will be less failure-prone than Hitachi's.

For all you storage fetishists fans, we've snapped a few pictures of the drives. Note that there's little physical difference between the 5,400- and 7,200-RPM drives from each manufacturer.

Hitachi's Travelstar 5K100 (left) and 7K100 (right) from above...

And below

Seagate's Momentus 7200.1 (left) and 5400.2 (right) from above...

And flipped