Dave Erickson writes:
> I've done a bit of searching and haven't come up with much but what I
> was wondering is: can a person load an entire OS into RAM from the HDD
> or network and then use a sync program to write updates to the disk
> but actually run the whole thing in ram?

You need to define what you mean by "OS".  The kernel always runs in RAM.
Userland programs such as "ls" are stored on the disk and loaded into memory
when run (by execve(2)).  You could copy everything from /usr to an
in-memory file system on boot.  While this would decrease latency when
running a program, the amortized latency would likely be much higher, as
many of the copied items will never actually be accessed.

Linux has a "buffer cache".  Blocks are typically read from the disk only
once and stored in the buffer cache.  Subsequent reads come from the buffer
cache.  Thus a program typically must only be read from disk the first time
it is run.

-- 
David Phillips <david at acz.org>
http://david.acz.org/


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