Re: document ext3 requirements

Theodore Tso
2009-01-04T22:06:57Z

On Sun, Jan 04, 2009 at 01:49:49PM -0600, Rob Landley wrote:
>
> Want to document the granularity issues with flash, while you're at it?
>
> An inherent problem with using flash as a normal block device is that the
> flash erase size is bigger than most filesystem sector sizes. So when you
> request a write, it may erase and rewrite the next 64k, 128k, or even a couple
> megabytes on the really _big_ ones.
>
> If you lose power in the middle of that, ext3 won't notice that data in the
> "sectors" _after_ the one your were trying to write to got trashed.

True enough, although the newer SSD's will have this problem addressed
(although at least initially, they are **far** more costly than the
el-cheapo 32GB SD cards you can find at the checkout counter at Fry's
alongside battery-powered shavers and trashy ipod speakers).

I will stress again, that most of this doesn't belong in
Documentation/filesystems/ext3.txt, as most of this is *not*
ext3-specific.

- Ted