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Auditing IPEAK SPT

Posted December 4th, 2001 by eugene

See also How We Test Drives

Testbed3: Auditing IPEAK SPT

The cornerstone of SR's new third-generation testbed is Intel's IPEAK SPT, a program that opens the way to unparalleled hard disk performance evaluation. The results delivered by IPEAK's tools are a bit startling; indeed, many readers refuse to accept the results since they don't align with long-held conceptions. More specifically, folks are used to the idea that SCSI hard drives, though highly optimized for random, non-localized, multi-user situations, always exhibit superior performance when compared to ATA drives even in desktop and single-user situations. As a result, when a manufacturer such as Western Digital pushes the envelope and delivers SCSI-like performance in an ATA drive with an 8-meg buffer and IPEAK results place it among the top SCSI drives for desktop performance, reception within the enthusiast community, ostensibly the target market for such a unit, is mixed. While many folks recognize that WD's latest drive truly is special, others imply that this showing "proves" that benchmarks can never really be accurate. It's time to let these misconceptions go! Such an argument begs premises from a preset conclusion, and that is irrational.

StorageReview.com's Desktop DriveMarks consist of trace files that were recorded utilizing IPEAK's WinTrace32. These files can then be analyzed using AnalyzeTrace and exactingly replayed through RankDisk. The recording-playback combination delivered by WinTrace32-RankDisk delivers us the amazing ability to recreate the disk accesses generated by any kind of system activity on a multitude of test drives. WinTrace32 intercepts all requests headed to the controller driver while RankDisk commences playback of these requests at the driver level. As a result, the CPU, RAM, OS, cache, and all other ancillary hardware and software impacts the playback once and only once, resulting in perfect recreation of high-level variables. Observe the following chain of a disk read or write: 

Application
     |
     |
     |
     V
Operating System
     |
     |
     |
     V
OS Disk Cache
     |
     |
     |
     V
OS File System
     |<-------- WinTrace32 records all that reaches this point ---> no overlap between
     |                                                              Wintrace32 & Rankdisk
     |<-------- RankDisk plays back all from this point onwards -------^
     V
OS Disk Host Adapter Driver
     |
     |
     |
     V
Disk Host Adapter
     |
     |
     |
     V
Hard Drive Buffer
     |
     |
     |
Hard Drive Platter

The perfect, non-overlap system delivered by WinTrace32 and RankDisk in theory delivers the best conceivable combination between controlled trials and relevant access patterns. The million-dollar question: Are we sure that WinTrace32 and RankDisk do exactly what they claim?

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