This development is exactly the kind of change that Jim clearly savored—so much so that in listening to his tribute, I began to wonder if he had thought of or published anything on flash-based storage prior to his disappearance. With the rapidly changing economics of flash, Jim would have had to be particularly insightful (at the time of his disappearance, flash was more than twice as expensive as it is now), but it seemed within the realm of possibility. His colleagues at Microsoft didn’t know of anything specific he had written on the topic, but directed me to his Web site for his list of papers. Thinking the published work was likely too old and that I had thus probably hit a dead end, I nonetheless went to the site—and what I saw there almost took my breath away: the second-most-recent link was “A Radical View of Flash Disks,” with a link to both a document and a talk. Thanks to the support of Jim’s family, we have been able to publish that paper, “Flash Disk Opportunity for Server Applications,” written with his colleague Bob Fitzgerald, in this issue. It is raw, and the numbers are now out of date—but Jim clearly sees the future in front of him, and it is a singular pleasure for the reader to be hoisted onto his shoulders.

Finding Jim’s work inspired us to add two other papers to this issue. First, since the time that Jim worked on this problem, one important impediment has been removed: the device-level issues that he describes—issues that have plagued consumer-grade flash-based SSDs (solid-state drives)—have been largely dealt with in the new class of enterprise-grade flash-based SSDs. It is important for practitioners to understand these problems and their solutions; STEC’s Pat Wilkison and Mark Moshayedi explain the innards of these important new devices in their article in this issue.

Second, in looking for other work that Jim might have done on flash, we ran across the work of Goetz Graefe, a Hewlett-Packard Fellow who had revisited Jim’s “five-minute rule” (the Jim Gray classic that we pointed to online in the May/June issue), wondering if flash had changed the equation. Goetz, too, saw Jim in this work (he dedicated this work to Jim), and it seems especially fitting that Goetz’s update of Jim’s rule now lives alongside Jim’s radical view of a flash-based future.

Enjoy this collection of articles—and the coming revolution in the storage hierarchy that they describe—and take a moment to mourn the loss of a great computer scientist who would have (once again) been in the thick of it all! Q

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BRYAN CANTRILL is a Distinguished Engineer at Sun Microsystems, where he has spent more than a decade working on system software, from the guts of the kernel to client code on the browser and much in between. Along with colleagues Mike Shapiro and Adam Leventhal, Cantrill designed and implemented DTrace, a facility for dynamic instrumentation of production systems that won the Wall Street Journal’s top Technology Innovation Award in 2006. In 2005, Cantrill was named by MIT’s Technology Review as one of the top 35 technologists under the age of 35, and by Info World as one of its Innovators of the Year. He received an Sc.B magna cum laude with honors in computer science from Brown University. © 2008 ACM 1542-7730/08/0700 $5.00