multiple MTD partitions

[Chris Ball]

Hi,

   >> Vs. goal 2: UBIFS write speed is about 70MiB/second, because of
   >> the write-back support. IOW, UBIFS is similar to traditional FSes
   >> like ext2, which have internal buffers and make writes fast. To
   >> compare, JFFS2 write speed on XO is about 1.3 MiB/s, because it is
   >> always synchronous.

   > I'm curious how you measured this, as the underlying hardware only
   > supports a max. transfer rate of around 20 MiB/s...

The "write-back" support mentioned above is describing a situation where
we write to a kernel cache and defer writes to the hardware until later.

JFFS2 does not do this, hence never getting *filesystem* write speeds
that are above the hardware limitation.  The 70MiB/second figure
describes writes as seen coming into the UBIFS filesystem, which
are not bound to the max. transfer rate of the hardware.

In short, the write speed for a filesystem does not have to be bound
by the underlying speed of flushing write buffers to hardware; in most
modern filesystem it isn't, although in JFFS2 it is.

- Chris.
-- 
Chris Ball   <cjb at laptop.org>