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SubjectRe: (reiserfs) Re: Implementing Meta File information in Linux (and a note at the end on current reiserfs status)
Richard Gooch wrote:

>
>
> Can you explain why you think that keeping the metadata in a normal
> file and splitting the data streams in userspace is going to be slow?

Imagine a million small pieces of metadata. Much better to make a directory out of it,and let the FS optimize the storage and indexing and caching and everything else.
The FS is not going to give your storage layer enough control via the VFS interface
for your storage to do its job as well as the FS could.

> I would have expected the file would have a "header" which describes a
> series of data streams, including file offsets. Putting the non-data
> metadata at the front would allow the normal data component to grow
> without any problems. Even if more metadata was added later, it would
> likely be small, so it could be easily cached and appended as the
> normal data grew. Accessing a particular stream is just a seek
> operation.

What about insertion? This is the killer issue...... Do you want to rewrite the entire1GB file to insert 100 bytes?

> Of course, if you have large metadata, then you're better off making
> each stream as a file in a directory and letting the FS do the work.
> The FS code already has one bunch of code to implement growing streams
> (files), I think we'd want to leverage that instead of implementing
> yet another level of what is effectively file/directory management
> inside the FS.
>
> Regards,
>
> Richard....




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