This is a good read:

http://www.cs.rochester.edu/meetings/sosp2003/papers/p125-ghemawat.pdf

And a more basic read (re-cap):

http://features.techworld.com/storage/467/googles-storage-strategy/

And some more fun:

http://static.googleusercontent.com/external_content/untrusted_dlcp/labs.google.com/en/us/papers/bigtable-osdi06.pdf


Oddly, I can not find any definitive claims that Googles DOES store everything in RAM. Do you happen to have some links? Everything I find is rather vague on the details. Only mentioning recent cache files and indexes being stored in RAM.

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car