Re: (reiserfs) Re: File systems are semantically impoverished compared

Hans Reiser (reiser@ceic.com)
Sun, 27 Jun 1999 00:22:46 +0000 (/etc/localtime)


Each layer with its own pointer structure adds additional pointers
because in a single tree system the depth of accesses is log N, but in a
two tree system the depth is 2 log(N/2), which is much more than log N.

Each layer of interface adds a layer of functionality distortion, and
the capabilities of a two layer system is in some ways the intersection
not the union of the separate capabilities of the layers.

Recovery is necessarily much uglified, more than twice as ugly, and this
makes performance worse since performance normally has recovery as the
primary crippling factor that prevents the use of various desired
algorithms.

Hans

Alexander Viro writes:
>
>
> On Sat, 26 Jun 1999, Hans Reiser wrote:
>
> >
> > The goal of reiserfs is not to get every person, who has invented yet
> > another namespace that can share the interactions it conducts with no
> > other namespace, to convert to reiserfs. The goal of reiserfs is to one
> > by one eliminate the reasons why these new namespaces keep getting
> > invented rather than using the filesystem namespace. I cannot
> > unify the namespaces, I can only somewhat reduce the reasons why they
> > fragment, and pontificate a bit at those who fragment them.
> >
> > Two filesystem layers are indeed terrible. What you are doing is not
> > analogous to, say, putting a file system ontop of a disk driver which is
> > ontop of a piece of hardware, no, you are writing a C interpreter in
> > Pascal. You are putting a motorcycle seat ontop of a truck chassis, and
> > then you are asking me to define why a truck chassis isn't as functional
> > as a motorcycle chassis, and given that you have already built a truck
> > chassis, you ask why it is that I think you won't have all the
> > functionality of a motorcycle using your motorcycle seat and handlebars
> > ontop of a truck chassis. What you want to do is like telling the TCP/IP
> > guys when they wrote TCP/IP that they should be using the serial line
> > driver as the bottom layer of their TCP/IP implementation, putting the
> > TCP/IP stuff in user space, and then preaching about the benefits of
> > increased portability to other Unixes that would result from that.
>
> Very colourful. What about a couple of technical arguments instead of
> Datamation-level analogies?

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