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IBM Ultrastar 36LZX DDYS-T18350
  June 7, 2000 Author: Eugene Ra  
Evaluation unit provided by ASL.


IBM owns the distinction of being second only to Seagate to enter the 10k RPM SCSI arena. Though the industry is perched on the verge of a transition to 15k RPM drives, 10k units still represent the bleeding edge of today's performance.

The year 2000 marks the fourth generation of 10k RPM hard disks. Over eight months ago, IBM held the distinction of being the first to announce 4th generation units, its Ultrastar 73 and 36LZX. Interestingly, it's only now that we're starting to see Big Blue's units enter the channel... months after Seagate's 4th generation Cheetah, a series who's announcement came after the Ultrastar.

The specs of the Ultrastar36LZX match those of the Cheetah 36LP/18XL series fairly well. Both units (as well as Quantum's Atlas 10k II) feature, of course, a 10k RPM spindle speed. Both the Cheetah and Ultrastar place 6.1 gigs of data on one platter, a bit less than the areal-density-leading Atlas, yielding a flagship capacity of 36.7 gigs. The model reviewed here, featuring 3 platters, stores a total of 18.4 gigs of data. IBM specifies a slightly swifter seek time - 4.9 milliseconds to the Cheetah's 5.2ms... though Quantum's unit trumps both with a 4.7ms seek. Like the Cheetah, the Ultrastar features a 4 meg buffer, half the size of the Atlas 10k II. An industry-standard 5 year warranty protects the drive.

Lets turn to's standard suite of benchmarks to determine where the Ultrastar 36LZX fits in the 10k hierarchy.

WB99/Win2k Low-Level Measurements

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Click here to examine the STR graph for this drive

WinBench 99 measures the Ultrastar 36LZX's access time at 8.5 milliseconds... perhaps just a tad higher than what should be expected given the drive's specified seek time of 4.9ms. The Ultrastar does manage to hold onto a 0.4ms lead over the Cheetah. The Quantum Atlas 10k II, however magnifies its supposed 0.2ms lead to a relatively hefty 0.7ms when under the scrutiny of WinBench.

IBM's drive brings up the rear of 4th-generation 10k RPM offerings when it comes to sequential transfer rates. In its outermost zone, the 36LZX manages 35 megs a second... lagging slightly behind the Cheetah's 36 MB/sec figure and quite a bit behind the Atlas 10k II's 40 MB/sec. Similarly, the transfer rate in the innermost zone of the Ultrastar, 23 MB/sec, trails the 25 MB/sec posted by its competitors.

WB99/Win2k WinMarks

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When it comes to the high-level Business and High-End Disk Winmarks, the Ultrastar 36LZX falls somewhere in between the Cheetah 18XL and the Atlas 10k II. The IBM manages to slide by the Seagate by margins of 3% and 5% respectively in the Business and High-End Winmarks. Big Blue's drive has no hope of catching Quantum's speedster, however... the Ultrastar trails the Atlas 10k II by 12% in the Business Disk Winmark and a whopping 22% in the High-End test.

Thus, if WinBench 99 is your most trusted measure of disk speed, the Atlas 10k II should remain your undisputed drive of choice. IBM's drive fails to displace the 10k II off its lofty perch (for that matter, the 15K RPM Cheetah X15 fails to do so too). IOMeter, however, will give us a better picture of relative disk performance. Let's investigate.

IOMeter Performance

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In an interesting testament to differences between benchmarks, IOMeter's hierarchy of drives is the reverse of that presented by WinBench 99. That is, Intel's benchmark rates the Cheetah 18XL as the fastest drive, the IBM trailing slightly behind, with the Atlas 10k II lagging further still.

Under a Linear Workstation load (admittedly a scenario too simplistic to occur in real-world usage), the Ultrastar 36LZX pulls ahead of the Cheetah 18XL by a margin of nearly 4%. On the other hand, under Very Light and Light loads, IBM's offering trails that of Seagate's by 4%. The differences narrow under Moderate and Heavy loads... in Moderate cases, the Ultrastar trails the Cheetah by 1%. Heavy loads result in a dead heat.

The 36LZX does get to flex its muscles in IOMeter when compared to the Atlas 10k II. In such a face off, the Ultrastar leads the Atlas by margins in many cases approaching 8%.

Though our focus is primarily on Workstation performance, we also keep performance figures for File Server and Database scenarios. In such cases, the IBM drive lags behind the offerings from Seagate and Quantum. For full details, check out the Database!


The UItrastar 36LZX continues the trend we've been witnessing towards quieter 10k RPM drives. Though its just a tad louder than the Cheetah 18XL (which, by the way, is an interesting reversal... IBM traditionally had the edge against the noisy Seagates), the 36LZX nonetheless brings relatively little seek noise to the table... certainly no worse than, say, the ATA Quantum Fireball Plus LM. Outside of a cooler, however, the drive operates quite warm to the touch in our midtower testbed. As should always be the case when dealing with 10k RPM drives, one should make sure the system case is well ventilated and/or active cooling is used.

-- The Safe Buy Award --

Simply put, this designation means we'd purchase this product without regret. Sure, there may be a slightly better, slightly faster, and/or slightly less-expensive model from a competitor, but you can't go wrong with this particular unit. This award is applicable, of course, to all units at the top of their class, but also applies to units that, though not quite best-of-class, provide a strong showing nonetheless.Despite its better seek time, though, Big Blue's drive doesn't quite deliver the speed necessary to take the throne from Seagate. IBM's latest 10k RPM drive brings performance to the table just short of the Cheetah 18XL, currently the fastest 10K disk we've tested. As most would realize however when dealing with margins that don't exceed 4%, the differences are quite small and probably not noticeable in most cases. Since IBM and Seagate both share excellent reputations and manageable heat levels, we find ourselves reverting to an increasingly common recommendation: go with whatever you find to be the least expensive.

IBM Ultrastar 36LZX DDYS-T18350
Estimated Price: $500
Also Available: DDYS-36950 (36.7 GB); DDYS-309170 (9.1 GB)
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