Re: Stacked file systems - why not and what instead?
Re: Stacked file systems - why not and what instead?
- Subject: Re: Stacked file systems - why not and what instead?
- From: Marek Kozubal <email@hidden>
- Date: Fri, 5 Mar 2004 21:44:56 -0500 (EST)
On Wed, 3 Mar 2004, Quinn wrote:
>
At 5:55 +0100 3/3/04, Ragnar Sundblad wrote:
>
>Apple Q&A 1242 says:
>
>
Marek did a fine job of answering your questions but, seeing as I
>
wrote the Q&A in question, I feel obliged to follow up with more
>
information.
Thanks! :)
>
Finally, I'd like to reiterate the comments I made in the Q&A. The
>
fact that Apple doesn't encourage or support stacking doesn't mean
>
that you can't do it. It just means that a) you can't get official
>
support from DTS, and b) you will probably suffer more binary
>
compatibility problems than if you were developing a supported
>
product. However, we have no secrets--the entire kernel source is
>
available via Darwin--and there's a variety of unofficial support
>
resources (such as this list). Marek is even using this technology
>
in a commercial product and he hasn't (yet) been abducted by the
>
Apple Kernel Purity Police (tm) (-:
I can vouch for this! (This made my day Quinn :) ) However, in version 2.0
of our product we are very likely going to switch to the style of WebDav's
file system for a number of reasons. One of them being that Apple has to
keep WebDav working, so anything we steal^H^H^H^H^Hborrow from there will
probably mirror into something in future variations of the VFS layer.
Also I have a much better understanding of whats going on at this layer
than when I started this project, which also helps...
One thing that I am worried about is how much of a speed hit one would
take having data going User -> Kernel -> User -> Kernel for a lot or most
of the file system calls. MIG RPC's clearly have a good amount of
overhead, and WebDav which I believe uses UNIX sockets, still seems like a
sluggish file system in general, though maybe http has more to blame on
that one than the boundary bounces. Any thoughts on this Quinn? :)
---
Marek Kozubal
email@hidden
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