Re: UBIFS vs Logfs (was [RFC PATCH] UBIFS - new flash file system)

[Artem Bityutskiy <dedekind@yandex.ru>]

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.

-- 
Best Regards,
Artem Bityutskiy (Артём Битюцкий)