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    SubjectRe: Transparent compression in the FS
    jw schultz wrote:
    >>Consider a simple key-value map, where "$hash $n" is the key and the
    >>value is the block of data. Only three operations need occur:
    >>* if hash exists (highly unlikely!), read and compare w/ raw data
    >>* write new block to disk
    >>* add single datum to key-value index
    > Nicely described, but each block now needs a reference count
    > which is incrmented if the raw compare yields a positive and
    > decremented when a reference to it receives a write.

    Yep. I'm pondering a sort of a closely-interconnected distributed cache
    for archival storage, so I have to care about refcounts on remote
    servers, too.

    > It may help to also have a reverse reference somewhere
    > from the block to the hash.

    I think I can avoid this...

    >>Inode block lists would need to be updated regardless of any collision;
    >>that would be a standard and required part of any VFS interaction. And
    > Under current schemes if i overwrite an already allocated
    > block of a file the block list need not be updated unless
    > the block is relocated. But that is a nit.

    Yep. For a networked filesystem, this is less annoying and clients will
    not normally notice any slowdown from this.


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      Last update: 2005-03-22 13:58    [W:3.425 / U:0.392 seconds]
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