Re: CacheFS

[Jan Kasprzak <kas@informatics.muni.cz>]

Jan Harkes wrote:
: > 	Every file on the front filesystem (NFS or so) volume will be cached
: > in two local files by cachefsd: The first one would contain the (parts of)
: > real file content, and the second one would contain file's metadata and the
: > bitmap of valid blocks (or pages) of the first file. All files in cachefsd's
: > backing store would be in a per-volume directory, and will be numbered by the
: > inode number from the front filesystem.
: 
: - Intermezzo uses 'holes' in files to indicate that content isn't
:   available.

	Well, but can you see the hole from the user-space daemon?

: - You might want to have a more hierarchical backing store, directory
:   operations in large directories are not very efficient.

	Yes, of course. But this is an implementation detail of cachefsd.

: - I believe you are switching the meaning of front and backend
:   filesystems around a lot in your description. Who exactly assigns the
:   inode numbers?

	Well, let's speak about NFS, locally cached on ext2. The present
implemetation takes inode number from NFS, and creates and ext2 file
named - for example - /cache/%d (for file contents) and  /cache/%d.attr for
stat(2) data and valid blocks bitmap. The %d is an inode number from the
NFS volume.

: Some references,
: 
: UserFS, PodFuk, AVFS,

	Thanks,

-Yenya

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\ Jan "Yenya" Kasprzak <kas at fi.muni.cz>       http://www.fi.muni.cz/~kas/
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