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    SubjectRe: Mis-Design of Btrfs?
    On Fri, 15 Jul 2011, Chris Mason wrote:

    > Excerpts from Ric Wheeler's message of 2011-07-15 08:58:04 -0400:
    >> On 07/15/2011 12:34 PM, Chris Mason wrote:
    > By bubble up I mean that if you have multiple layers capable of doing
    > retries, the lowest levels would retry first. Basically by the time we
    > get an -EIO_ALREADY_RETRIED we know there's nothing that lower level can
    > do to help.

    the problem with doing this is that it can end up stalling the box for
    significant amounts of time while all the retries happen.

    we already see this happening today where a disk read failure is retried
    multiple times by the disk, multiple times by the raid controller, and
    then multiple times by Linux, resulting is multi-minute stalls when you
    hit a disk error in some cases.

    having the lower layers do the retries automatically runs the risk of
    making this even worse.

    This needs to be able to be throttled by some layer that can see the
    entire picture (either by cutting off the retries after a number, after
    some time, or by spacing out the retries to allow other queries to get in
    and let the box do useful work in the meantime)

    David Lang

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      Last update: 2011-07-15 18:27    [W:0.037 / U:1.200 seconds]
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