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    SubjectRe: [ANNOUNCE] Ramback: faster than a speeding bullet
    On 2008-03-10T09:37:37, Alan Cox <> wrote:

    > Why - your chunks simply become a linked list in write barrier order.
    > Solve your bitmap sweep cost as well. As you are already making a copy
    > before going to backing store you don't have the internal consistency
    > problems of further writes during the I/O.

    You get duplicated blocks though. But yes, I agree - write-backs to the
    disk must be ordered, other it's going to be too unreliable in practice.

    An in-memory buffer for a log-structured block device.

    > Yes you may need to throttle in the specific case of having too many
    > copies of pages sitting in the queue - but surely that would be the set of
    > pages that are written but not yet committed from a previous store
    > barrier ?

    You could switch from a journal like the above to a bitmap when this
    overrun occurs. (Typical problem in replication.) SteelEye holds a
    patent on that though, as far as I know.


    Teamlead Kernel, SuSE Labs, Research and Development
    SUSE LINUX Products GmbH, GF: Markus Rex, HRB 16746 (AG Nürnberg)
    "Experience is the name everyone gives to their mistakes." -- Oscar Wilde

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