ERIC BREWER
Q. How much are people willing to pay?
A. I think if you reduce the footprint, you can argue that people
would pay a lot more, because we are already buying 4 gigabyte disks instead
of nine gigabytes because we dont need the capacity. We are not
opposed of paying the price of the 9s, its just that they dont do anything
for us. People paid 2x or more for RAID for a long time, and what
I am suggesting offers them a lot more than RAID. I do not know how
much.
Q. What read write ratios do you encounter and how does this factor
affect the search engine?
A. It depends a lot on the application. In search engines
there is a probably a ratio of 100 to 1 for reads to writes. For
cache its actually slightly more writing then reading. Because youll
write stuff that youll never read again. But we dont know yet what
the actual ratio is but it is much more even. In that game theres
other tricks you can play such as typically you master copy any piece of
data which means its okay for the disk to lose data as long as it doesnt
corrupt it. Which really changes the games that you play, which is
probably the reason we can get away without having RAID, because we dont
care about lost data we just dont want get corrupted data. We can
avoid that with checksums and basically run the disk full tilt, and when
we loose them, we have to recover but its not that bad.
Q. Your search engine would seem to be unique for a different
application since you have all of your eggs in one basket. What is
your disaster recover operation?
A. Our disaster recovery is probably better than what most business
have already. For example we were not affected by the San Francisco
electrical issues. And so any one using the Santa Clara cluster was
automatically moved to the Virginia cluster. That cluster would then
reduce its database size automatically to allow that cluster to handle
the essentially unexpected increase in total queries having to be served.
That has been tested slightly but basically the bottom line is our up time
is .99999 and I think we would transfer over to quite naturally to the
Virginia cluster in the event of an earthquake. Thats certainly
the plan. You have to go to extensive testing to keeps these things
working. Certainly at his point I think our customers do demand certain
kinds of stuff your talking about. Certainly YAHOO would be furious
if our back end were down and they couldnt deliver searches to their customers.
Microsoft has contractual obligation on us in terms of up time and reliability
as well.