A Conversation with Jim Gray
Dave Patterson interviews Jim Gray about the future of storage (via Tim Bray). Highly recommended.
DP So disks are not random access any more?
JG That’s one of the things that more or less everybody is gravitng toward. The idea of a log-structured file system is much more attractive. There are many other architectural changes that we’ll have to consider in disks with huge capacity and limited bandwidth.
JG The Internet plans to be running at gigabit speeds, but if you experiment with your desktop now, I think you’ll find that it runs at a megabyte a second or less.…That translates to 40 gigabytes per hour and a terabyte per day. I tend to write a terabyte in about 8 to 10 hours locally. I can send it via UPS anywhere in the U.S. That turns out to be about seven megabytes per second.
DP Wouldn’t it be a lot less hassle to use the Internet?
JG It’s cheaper to send the machine. The phone bill, at the rate Microsoft pays, is about $1 per gigabyte sent and about $1 per gigabyte received—about $2,000 per terabyte. It’s the same hassle for me whether I send it via the Internet or an overnight package with a computer. I have to copy the files to a server in any case. The extra step is putting the SneakerNet in a cardboard box and slapping a UPS label on it. I have gotten fairly good at that.
JG What I mean by that is [a disk is] going to have a gigahertz or better processor in it. And it will have a lot of RAM. And they will be able to run almost any piece of software that you can think of today. It could run Oracle or Exchange or any other app you can think of.
In that world, all the stuff about interfaces of SCSI and IDE and so on disappears. It’s IP.
Further reading: The Design and Implementation of a Log-Structured File System.
