disk scheduling (was: Re: RFC: adding 'proxy' nodes to provider ports (with patch))

[Ivan Voras]

2009/3/22 Poul-Henning Kamp <phk at phk.freebsd.dk>:
> In message <eb21ef440903211800h266ec0aes158cb189095289c1 at mail.gmail.com>, Luigi
>  Rizzo writes:
>
>>The thread was meant to be on inserting transparent nodes in GEOM.
>>
>>Scheduling was just an example on where the problem came out,
>
> Scheduling is the *only* application I have seen mentioned for
> this special case geom construct ?

I've joined this thread because once upon a time I was working on what
has grown into gjournal, and one aspect of the original project was a
logging "safety net" mode. The idea was to insert this class (or
whatever) just before a file system consumer then do risky things with
the file system metadata (like fsck-ing a badly damaged file system),
with the option of commiting it or rolling it back. It has even grown
into another SoC project.

I see now it doesn't comply with my idea of a "lightweight" proxy (the
first item, about 1:1 mappings) - so proxies look more and more like
they should be classes.

Also, gcache looks like a candidate.