On Saturday 02 February 2002 12:41, Terrence Brannon wrote:
> Has anyone taken some sort of shared disk (ie, NFS) and used it
> to share the cache among AxKit servers?
>
> This might create an n-fold speedup.
>
Well, I thought about it, and my answer is no...

Assume you cache something once and fetch it back many times (otherwise 
what's the use of a cache). If you load balance 2 web servers, you now have 
2x the number of cache misses (cause each server has to build its own cache) 
but the same number of cache HITS (minus one). So if you had 100 hits with 
one server the ratio would be 99:1, with two servers 98:2, etc. The point is 
that that one extra page generation is not a big deal vs the existing cache 
speedup. 

The down side is that nfs is slow compared to local disk, and so your entire 
cache takes a hit, plus reliability suffers, and there might even be 
concurrency issues involved with cache writes.

I'm not likely to try it. I might nfs serve my CONTENT with a cluster of web 
servers and a file server. If the file server is very fast it can work, but 
usually highly loaded systems are IO bound, and that means you need MORE disk 
drives working harder, not less drives on the other sides of slow lan 
connections. 

> <hacker language="Perl" type="AxKit" uniqueness="just another">
> Terrence Brannon
> </hacker>

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