by November 11, 2000 0 comments

Seagate has once again upped the ante with its latest hard
drive–the Cheetah X15. Perhaps the most noticeable new feature of this drive
is its 15,000-rpm spindle rotation speed. Till now, we had mostly been seeing
5,400 and 7,200 rpm IDE drives, and 10,000 rpm SCSI drives. High-spindle speeds
translate into higher transfer rates.

However, spindle speeds alone don’t determine the transfer
capacities of a hard drive. In real world situations, the heads have to move
around a lot to position themselves over the tracks from which data is to be
read. The time taken to do this is called the seek time. After the head has been
placed over the appropriate track, it must wait for the right sector to move
under it so that it can start reading or writing data. This is called rotational
latency and is inversely proportional to the spindle speed.

Seagate Cheetah X15 ST318451LW 

SCSI hard deive.
Features: 15,000 rpm; Ultra160 SCSI interface; 4 MB cache; 3.9 ms seek
Pros: Very high transfer rates and spindle speeds; low seek time. 
Cons: None
Source: ACI Computers
 7/13, First Floor, Kalkaji Extension. New Delhi 110019. 
Tel: 11-6287551 
Fax: 91-11-6287553 

We know that the Cheetah X15 has an excellent spindle speed,
but what about the seek time? To lower the seek time; Seagate has reduced the
size of the platter so that the head has to move less. This results in a rated
seek time of 3.9 ms.

The hard drive has an Ultra160 SCSI connector, which can give
burst transfers of 160 MB per sec. It also has 4 MB cache for storing temporary
data, which can greatly boost drive throughputs. The total formatted capacity of
the hard drive is 18.35 GB.

Now for the tests. We used a PIII/800 MHz system with 128 MB
RAM, a Creative GeForce display card, and an Adaptec AHA-2940U2W SCSI card. We
tested the drive mainly for raw throughputs to see how it performs compared to
other SCSI drives that we have recently tested.

The X15 certainly beat most of the SCSI drives we’ve tested
so far. The average transfer rates stood at an amazing 37 MB per second. In
comparison, the Cheetah XL had managed 35.5 MB per second and the Atlas 10K 25.8
MB per second. The average disk-access time was 4.59 ms for the X15, 6.13 ms for
the XL and 5.66 ms for the Atlas 10K. The X15 managed to excel in processor
utilization as well, just 1.7 percent which was bettered only by the Quantum
Atlas 10K at 1.44 percent.

After our tests, the drive had warmed up quite a lot, but
this is normal for a SCSI drive. However, it’s always recommended to have
well-ventilated cabinets for such high-speed drives. Overall, the performance of
the drive has been the best so far.


Avg transfer
rate (kB per sec)

time (ms)
utilization (%)
Cheetah X15 36,900 4.59 1.7
Cheetah XL 35,550 6.13 4.05
Atlas V 29,750 7.39 3.78
Atlas 10K 25,800 5.66 1.44

Anuj Jain at PCQ Labs

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