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    SubjectRe: UBIFS vs Logfs (was [RFC PATCH] UBIFS - new flash file system)
    On Tue, 1 April 2008 11:45:56 +0300, Artem Bityutskiy wrote:
    > Tomasz Chmielewski wrote:
    > >For me, the motivators to wait for LogFS are mainly the facts that it
    > >can work on traditional block devices, and not only on pure flash:
    >
    > Sorry Thomasz, for me this makes zero sense. There are _much_ better file
    > systems for block devices. UBIFS may work on top of a block device as
    > well (just needs few hacks to make it possible) - it is not a problem
    > at all, it is just _senseless_.
    >
    > JFFS2/UBIFS/LogFS is a separate _class_ of file-systems. The are designed
    > for _flash_, which has completely different work model then block device.
    > They are _native_ flash file systems.
    > Here are more details:
    > http://www.linux-mtd.infradead.org/faq/general.html#L_mtd_vs_hdd
    >
    > The traditional FSes _cannot_ work on top of flash. The solution for this
    > is using FTL, which emulates a block device on top of flash. It _hides_ the
    > real device, and fakes a block device for you. And you can use traditional
    > FSes on top of that fake block device.
    >
    > The whole _point_ of this separate class of FSes is because we believe
    > we may do much _better_ job if we use flash _natively_, instead of using
    > FTL. FTL is the place where you loose performance, reliability, and so on.
    >
    > And you are saying about using a native flash FS on top of a block device
    > like an SD card. This is just not sane: SD card first emulates a block
    > device
    > for you, looses performance at this point, then you again emulate a flash
    > on top of this, and suffer from this again.

    About a year ago I would have used roughly the same argument. But in
    the meanwhile I have accepted the fact that any piece of flash I'll use
    in a notebook in the next five years will likely use SATA or USB as a
    transport medium.

    Jörn

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