June 11, 2001

Review: Seagate Cheetah 36XL SCSI drive

Author: JT Smith

- By Jeff Field -

With 15,000-RPM drives now on the market, the price of 10,000-RPM SCSI drives is sure to fall. This will allow
those looking for high-end performance to get what they want at a price that won't break the bank. Today, I review
the latest generation of the first 10,000-RPM drive I can remember: Seagate's 18-gigabyte Cheetah 36XL.The Seagate drive I'm testing today is the 18.2-gigabyte Ultra160 10,000 RPM Cheetah (ST318405LW). The drive
itself isn't much different from most SCSI drives on the market now. The company claims the drive is 15 percent faster than earlier
models. There are two things that I remember about the first SCSI drive I had -- a 9-gigabyte Seagate Barracuda: it was a half-height drive that needed lots of room for its large amount of heat, and it was loud. Performance has
come a long way since then. SCSI drives now, while not quite reaching the levels of IDE drives, are much quieter, smaller
and cooler than they used to be.

In some ways, SCSI has gotten the short end of the stick; while the drives are essentially the same as IDE, SCSI drives cost much more, relegating it to the role of a niche market player. It
takes someone with a very specific purpose in mind to justify paying nearly a thousand dollars for a SCSI drive that has
an equivalent IDE drive priced at $200. This is why SCSI drives are generally beyond the person building a PC for
personal use -- most people simply don't need it. Those who do, however, have many different drives to choose from, including this offering from Seagate. The sort of people who need SCSI are those who
have multiple disk drives performing many tasks at once. SCSI allows more
than one device to issue commands at the same time. In IDE drives, only one
command can be issued -- say, a read command on a CD-ROM. This means that the
other devices have to wait for that command to be sent before they can go along
doing their own thing. In SCSI, multiple commands may be sent, making it much
more efficient for multitasking and having multiple drives.

Specs
Name Cheetah 36XL
Model ST318405LW
Form Factor Low Profile
Formatted Capacity 18.352 Gigabytes
Platters 2
Spindle Speed 10,022 RPM
Interface Ultra160

Thanks to the number of platters on this drive, it runs relatively quiet and cool. I was impressed, as the 36XL
is one of the few SCSI drives I have tested that are not hot to the touch, but rather just warm. I suspect,
with adequate empty space around it, the Cheetah 36XL could run quite reliably without the need for separate cooling. As for
noise, an important factor when picking a drive for a workstation, the 36XL is quiet for a SCSI drive -- but not nearly as hushed as today's average IDE storage devices, which
are at times practically inaudible. Normal operation causes noise that gets louder and then softer in a cycle. As
it turns out, this is a feature on these drives, thanks to a rotational
vibration sensor that monitors the vibration caused by
the presence of more than one active drive. The goal of this sensor is to stop
the drive from having to make another pass to pick up data missed due to excessive
vibration.

Performance
For those looking for the best combination of performance and capacity in SCSI drives, 10,000 RPMs would seem to be the
best market at this time. Presently, the faster 15,000 RPM drives only have small capacities, up to 18 gigabytes, while
10,000-RPM drives such as the 36XL can be found in sizes up to 73 gigabytes. If capacity is needed as well as
performance, the 10,000-RPM drives are going to be where you find such a combination, but just how fast is fast enough?

System Configuration
AMD Athlon 750
128 Megabytes PC133 SDRAM
3COM 3C905TX-B 10/100MB NIC
3DFX Voodoo 3 3000 AGP 16MB Video Board
Adaptec 3200s or 29160 32-BIT PCI SCSI Controller
Western Digital 10gb 7200 RPM WD102BA IDE HDD (boot/OS) (ext2)
Red Hat Linux 7.1 - Kernel 2.4.5 with Adaptec dpt_i2o patch
Seagate 18 gigabyte 10,000 RPM Ultra160 Cheetah Drives

bonnie++ results
Bonnie++ is a hard drive benchmark that tests the writing and reading
from both a single large file (such as that of a database) and many small files (like a proxy, or mail program). It is
useful for simulating performance under such applications.

Bonnie++ Results
Sequential Output
Controller Per-Character Block Rewrite
Adaptec 3200s 8930 K/sec, 99% CPU 25991 K/sec, 34% CPU 8613 K/sec, 8% CPU
Adaptec 29160 9265 K/sec, 99% CPU 26562 K/sec, 48% CPU 7191 K/sec, 7% CPU
Sequential Input Random
Controller Per-Character Block Random
Adaptec 3200s 8234 K/sec, 79% CPU 31238 K/sec, 20% CPU 207.3 Seeks/sec, 1% CPU
Adaptec 29160 9753 K/sec, 89% CPU 36119 K/sec, 20% CPU 248.1 Seeks/sec, 2% CPU
Sequential Create
Controller Create Read Delete
Adaptec 3200s 10528 /sec, 100% CPU none 13189/sec, 99% CPU
Adaptec 29160 10415 /sec, 99% CPU none 12844/sec, 100% CPU
Random Create
Controller Create Read Delete
Adaptec 3200s 10137 /sec, 99% CPU none 10090/sec, 90% CPU
Adaptec 29160 9724 /sec, 94% CPU none 11215/sec, 99% CPU

The bonnie++ the results seem comparable to Seagate's claims -- for input, we see a speed of 36119K/sec, slightly
below the claimed speed of 43MB/sec. The read speed, for some reason, clocked in a bit lower at 26,562 or so, which may be
due to the way bonnie++ reads data, attempting to simulate database access.

hdparm results
The hdparm tests give you the raw throughput of the device -- essentially, the best you can possibly hope for. Uncached is
the buffered speed of the disk, without the use of the operating system cache. Cached results test the perform of the RAM
and CPU more than they test the drive itself.

hdparm -t (Uncached)
Results
Adaptec 3200s 36.47 MB/sec
Adaptec 29160 33.33 MB/sec
hdparm -T (Cached)
Results
Adaptec 3200s 112.28 MB/sec
Adaptec 29160 111.30 MB/sec

Here we see the drive coming close to the rated 43MB/second, coming in at 33MB/sec on the 29160 controller and 36MB/second
on the 3200s. Even though the drive seems to perform slightly lower than advertised, it is still much faster than any
comparable IDE drive.

Conclusion
The Seagate 36XL is targeted for the workstation market, and is an excellent drive for its market. Odd
noises aside, the 36XL brings speed, quiet and reliability into one drive. With
a five-year warranty, Seagate makes it clear that these drives are built to last: The 36XL is a drive that is meant to run
reliably for extended periods of time. The only problem may be that
today's workstations need more space than this specific 18-gigabyte model can offer, but the higher-capacity 36XL models
should perform at the same level, or even (in some cases) slightly better. If you are looking for an affordable SCSI hard drive, the 18-gigabyte is available for $225 on Price
Watch
. In the market for 10,000-RPM drives, you're not going to find any drives that blow each other out of the
water, so the real tests are all about price and reliability. If you're in need of SCSI storage, the 36XL is a choice that
performs well for a decent price.

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