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Seagate Cheetah 18LP AV ST318233LWV
  April 4, 2000 Author: Eugene Ra  
Evaluation unit provided by Seagate Technology.


These days we're on the threshold of the fourth-generation 10,000rpm disk, with drives from Seagate already readily available from many resellers and units from Quantum and Big Blue in the wings. These drives feature the latest in areal density, packing upwards of 7 gigs onto a single 3" platter. Recently, however, Seagate re-released its third-generation Cheetah 18LP, updated with an Ultra160/m SCSI interface and a larger buffer.

As a third-generation unit, the 18LP AV features 3 gigs of data per platter. Combined with its six-platter construction, the drives sports an 18.2 GB capacity. Its rated seek time, however, is just as fast as Seagate's fourth-generation units at 5.2 milliseconds. The standard 18LP features a one meg buffer. The AV version, on the other hand, features four megs of cache, matching today's units. The fact that all other mechanics remain identical, however, allows for an interesting opportunity to gauge the effects of buffer size on overall performance. The 18LP AV features an enterprise-class 5-year warranty.

The Cheetah 18LP AV is one of the first drives to receive an individual review following the rollout of our new testbed. As a result, we're providing figures collected on both the new and old systems. We'll continue to do so for an interim period before phasing out the old testbed entirely.

WB99/Win2k Low-Level Measurements

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Click here to examine the STR graph for this drive

The Cheetah 18LP AV posts average access times right on par with the latest-generation Cheetah 36LP, just as we'd expect from two drives that feature the same spindle speed and seek time. Sequential transfer rates, however, are where the 18LP AV falls behind. Its lower linear data density causes it to lag behind its younger brother by 22%.

WB99/Win2k WinMarks

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The Business Disk WinMark 99 run under Windows 2000 shows the Cheetah 18LP AV lagging behind the Cheetah 36LP by a rather negligible 2% margin. The High-End WinMark, in the past always a bit more sensitive to sequential transfers, places the 18LP AV behind the 36LP by a more substantial 9%.

IOMeter Performance

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The Cheetah 18LP AV's similar access time and presumably similar firmware allow it to keep right up with the Cheetah 36LP in our IOMeter tests. The largest difference exhibited under a Workstation Access Pattern is at a Medium Load, where a 3% gap exists. The gap narrows in all other cases.

Legacy Tests

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Compared to the Cheetah 36LP, the Cheetah 18LP AV does quite well in our old-testbed comparisons. The Business Disk WinMark 99 run in either Windows 95 or Windows NT 4.0 reveals comparable performance between the two drives with the 18LP AV actually pulling ahead, albeit by a miniscule 1%. The High-End Disk WinMark 99, however, places the 36LP ahead with the 18LP AV falling behind by margins of 4%-9%.

 Testbed I  Ziff Davis WinBench 99 under Windows 95 OSR 2.1 using FAT 32  Testbed I 
Benchmark Seagate Cheetah 18LP (18.2 GB U2W-SCSI)Seagate Cheetah 18LP AV (18.2 GB Ultra160/m SCSI)
Business Disk WinMark 99 (KB/sec) 3813 4157
High-End Disk WinMark 99 (KB/sec) 13133 14767
AVS/Express 3.4 (KB/sec)8770 10500
FrontPage 98 (KB/sec)38967 39367
MicroStation SE (KB/sec)12533 14867
Photoshop 4.0 (KB/sec)11300 11400
Premiere 4.2 (KB/sec)9890 11933
Sound Forge 4.0 (KB/sec)18033 20467
Visual C++ (KB/sec)14633 15200
Disk/Read Transfer
Beginning (KB/sec)27800 27967
End (KB/sec)17367 17500
Disk Access Time (ms)9.31 9.3
Disk CPU Utilization (%)5.66 5.62

 Testbed I  Ziff Davis WinBench 99 under Windows NT 4.0 using NTFS  Testbed I 
Benchmark Seagate Cheetah 18LP (18.2 GB U2W-SCSI)Seagate Cheetah 18LP AV (18.2 GB Ultra160/m SCSI)
Business Disk WinMark 99 (KB/sec)4343 4640
High-End Disk WinMark 99 (KB/sec)13767 14333
AVS/Express 3.4 (KB/sec)19167 19833
FrontPage 98 (KB/sec)35867 35867
MicroStation SE (KB/sec)19100 20367
Photoshop 4.0 (KB/sec)7717 7853
Premiere 4.2 (KB/sec)11233 11800
Sound Forge 4.0 (KB/sec)12033 13067
Visual C++ (KB/sec)13333 13933
Disk/Read Transfer
Beginning (KB/sec)28100 28100
End (KB/sec)17500 17500
Disk Access Time (ms)9.15 9.1
Disk CPU Utilization (%)2.67 2.55

A more interesting comparison arises when contrasting the Cheetah 18LP AV with the original Cheetah 18LP. Regular SR readers may recall an article we published last year comparing a Maxtor DiamondMax Plus 5120 featuring a 512k buffer with the same drive featuring 1 meg of cache. The differences proved to be negligible.

Such is not the case, however, when it comes to the 18LP AV vs. the original 18LP (at least according to WinBench). Here we find that though both drives share identical low-level measurements, the 18LP AV displays substantial improvements when it comes to the higher-level WinMarks.

The Business Disk WinMark 99 run in either Windows 95 or NT 4.0 places the 18LP AV ahead of the 18LP by margins of 7%-9%. High-End Disk WinMark differences are also pronounced, the 18LP AV being just 4% faster in NT but a substantial 12% swifter in Win95.

The question is begged: What's different in this situation that creates these noticeable differences when no such distinction could be made with the DiamondMax Plus tests? Here's a list to chew on:

  • 2x difference between the DiamondMaxes; 4x difference between the Cheetahs
  • ATA DiamondMaxes; SCSI Cheetahs (we don't believe this would be a factor, however)
  • The DiamondMaxes had the same interfaces, both being ATA-33; the Cheetahs differ with the 18LP featuring an Ultra2 interface while the 18LP AV is an Ultra160/m drive
  • Firmware unchanged in the larger-buffer DiamondMax; Firmware specifically tweaked in the 18LP AV to take advantage of the larger buffer?


We're not exactly clear why Seagate re-released the 18LP AV in a 160/m configuration. We've heard some rumors that the 18XL/36LP series experienced delays and thus the 160/m 18LP AV was forced to hold over performance-oriented users. More likely, however, is that Seagate still has quite a few 3 gig platters left over from last generation. So, instead of selling users the same old drive simply because the parts are lying around, why not at least update the interface to something more current? This looks like the path Seagate chose.

At any rate, the competent performance that this year-old design turns in once again goes to show that sequential transfer rate is relatively unimportant in the majority of everyday applications. In most cases (IOMeter, WinBench 99 Business Tests), the 18LP AV keeps right up with the newer 36LP. Thus, the Cheetah 18LP AV may very well be a contender for performance-oriented users especially if the price is favorable compared to current generation models.

Seagate Cheetah 18LP AV ST318233LWV
Estimated Price: $599
Also Available: ST39133LWV (9.1 GB)
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