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    SubjectRe: [RFC PATCH 0/5] Btrfs: Add hot data tracking functionality
    Hola Everybody;
    On the 04.08.2010 19:40, Mingming Cao wrote:
    > On Thu, 2010-07-29 at 22:17 +1000, Dave Chinner wrote:
    >
    >> On Wed, Jul 28, 2010 at 03:00:48PM -0700, Mingming Cao wrote:
    >>
    >>> On Wed, 2010-07-28 at 01:38 +0200, Christian Stroetmann wrote:
    >>>
    >>>> At the 28.07.2010 00:00, Ben Chociej wrote:
    >>>> Wouldn't this feature be useful for other file systems as well, so that
    >>>> a more general and not an only Btrfs related solution is preferable?
    >>>>
    >>>>
    >>> Would certainly nice to add this feature to all filesystem, but right
    >>> now btrfs is the only fs which have multiple device support in itself.
    >>>
    >> Why does it even need multiple devices in the filesystem? All the
    >> filesystem needs to know is the relative speed of regions of it's
    >> block address space and to be provided allocation hints. everything
    >> else is just movement of data. You could keep the speed information
    >> in the device mapper table and add an interface for filesystems to
    >> query it, and then you've got infrastructure that all filesystems
    >> could hook into.
    >>
    >> The tracking features dont' appear to have anything btrfs specific
    >> in them, so t iseems wrong to implement it there just because you're
    >> only looking at btrfs' method of tracking multiple block devices
    >> and moving blocks....
    >>
    >>
    >
    > I agree hot data tracking could be done at vfs layer. The current hot
    > data temperature calculation and indexing code is very self-contained,
    > and could be reuse to other fs or move up to vfs. We could define a
    > common interface to export to hot data tempreture out. The relocation
    > eventually has to be filesystem specific. btrfs does cow and knows where
    > is the data on/off SSD directly makes the relocation to and from very
    > straightforward.
    >
    >

    Thanks for your thumb up. But maybe other interested persons should also
    point their thumbs up at first before investing the effort of its
    implementation. I mentioned this feature, because it is a trend that got
    momentum in the area of (storage) virtualization and in this way in the
    fields of cloud computing and service computing as well.

    And: My both thumbs are already up. :D

    > Mingming
    >
    >

    Christian *<:o) O>-< -(D)>-<


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