Erik’s point, which is that today people don’t know why they’re using RAID. It may very well be the same with flash.

GReG GanGeR: The general model of search engines is you want to have a certain cluster that handles a given load. When you want to increase the load you can handle, you essentially replicate that entire cluster. It’s the unit of replication that makes management easier.

When it’s Christmas Eve and the service load is low, you could actually power down many of the replicas. While I do not believe this has been done yet, it seems like the thing to do as power costs continue to be a larger issue. In these systems there is already a great degree of replication in order to provide more spindles during high-load periods.

 

mache cReeGeR: You all said that there is low-hanging fruit to take advantage of. Are there things you can do today as profound as server virtualization?

steVe KLeiman: The companion to

server virtualization is storage virtualization. Things like snapshots and clones take whole golden images of what you’re going to run and instantaneously make a copy so that only the parts that have changed are additional. You might have 100 virtual servers out there with what they think are 100 images, but it’s only one golden image and the differences. That’s an amazing savings. It’s the same thing that’s going on with server virtualization; it’s almost the mirror image of it.

What has come about over the last few years is the ability to share the infrastructure. You may have one infrastructure, but it’s still a hundred different images, you’re actually not sharing the data. That’s changed in the last five years since we have had cloning technology. This allows you to get this tremendous so-called thin-provisioning savings.

eRic BReWeR: I disagree with something said earlier, which is that it’s becoming hard to delete stuff. I feel that deletion is a fundamental human right

because it gets to the core of what is private and what rights you have over data about you. I want to be able to delete my own stuff, but I also want to be able to delete from groups that have data about me that I no longer trust. A lot of this is a legal issue, but I hate to feel like the technical things are going to push us away from the ability to delete.

steVe KLeiman: That’s a good point.

While it’s hard to expend the intellectual effort to decide what you want to delete, once you’ve expended that effort, you should be able to delete. The truth is that it’s incredibly hard to delete something. Not only do you have to deal with the disks themselves, but also the bits that are resident on the disk after you “delete” them, and the copies, and the backups on tape.

One of the things that is part of our product right now, and which we continue to work on, is the ability to fine-grain encrypt information and then throw away the key. That deletes the information itself, the copies of the in-

 

invented by iBm in 1956, the first model 350 disk drive contained 50 24-inch diameter disks and stored a total of 5mB. iBm later added removable disk platters to its drives; these platters provided archival data storage.

PHO TOGRAPH BY MARK RICHARDS, FROM THE BOOK CORE MEMORy, CHRONICLE BOOKS