[wplug] disk:ram ratios

James O'Kane jo2y at midnightlinux.com
Fri Nov 16 12:01:39 EST 2001

Does anyone know of a website where they talk about good disk to ram 
ratios? I have a file server that is almost constantly at a load of 6-9. 
My guess is the machine doesn't have enough ram for disk buffers. Based 
on the load and what processes are running (mostly nfs) I think there are 
5 or more processes trying to read disk at any one time. If I understand 
it correctly, the kernel and disk will read ahead and preload data that 
will most likely be asked for next. My theory is that one process does 
its read and creates a cache, the next 5 do the same thing and the cache 
of the first process gets flushed before it does a read again. In effect 
cancelling any buffering effects. So I'm looking for any sites that have 
tested this type of thing?

The simple answer would be to just throw as much ram as I can in, but 
businesses usually want you to justify the need before they spend money on 
hardware :)

If it matters, the machine has 1 gig of RAM and 740gig of disk.


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