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From "Vadim Gritsenko" <vadim.gritse...@verizon.net>
Subject RE: Caching and key collision?
Date Tue, 15 Jan 2002 18:21:43 GMT
> From: Berin Loritsch [mailto:bloritsch@apache.org]
> 
> Kuhnle@heinrich-partner.de wrote:
> 
> >
> > Hi,
> >
> > I noticed caching is done by generating a key with generateKey. This
> > returns a long, which is commonly generated through hashing. The
> > documentation says "This key must be unique inside the space of this
> > component", which hashing does not guarantee. Won't this lead the
cache
> > to confusing two different cacheable objects (files/server
pages/etc.)
> > which accidently have the same cache value? This sure is an unlikely
> > event, but ist still can happen. Also, on pipelines with many
program
> > steps, the cache generates very long file names some operatings
systems
> > can't cope with.
> 
> 
> Regarding the last issue, I have been a victim of that.  Windows 9x
> cannot handle the long filenames generated by the cache.
> 
> However, Windows NT and just about every Unix can, so to me this is a
> minor issue--who in their right mind would want to serve anything from
> Windows?
> 
> 
> A more fundamental issue however is in regards to how quickly an OS
> 
> is on seeks.  Windows favors shallow directories and large numbers of
files
> in a directory.  UNIX favors deep directories and small numbers of
files
> in a directory.
> 
> When you go to the extreme that each does not like, you *really*
notice
> the slowness.  I have had my Windows machine block for 15 seconds at a
> time while navigating very deep hierarchies (this is especially true
on
> Win 9x).  Again, while working on a Perl webapp that cached info on
the
> drive, Linux would pause for a few seconds (5-6) when there were about
> 1000 entries in a directory before displaying the contents of the
directory.
> 
> If we could tune our cache to favor what the OS favors, it would add
> just that extra something to make the cache even faster.

Have you seen Gerhard's JispFilesystemStore? It promises to solve issue
on both platforms, on Win as well as on *NIX.

Vadim


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