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Re: [ts-7000] Re: ts-7000 in unattended embedded service

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Subject: Re: [ts-7000] Re: ts-7000 in unattended embedded service
From: Jim Jackson <>
Date: Tue, 16 Aug 2005 17:12:26 +0100 (BST)

On Tue, 16 Aug 2005, Jesse Off wrote:

> IIRC, EXT3 implements a meta-data journal that should guarantee that
> the filesystem doesn't trash itself, but you can still end up
> loosing bits of the files that were being written to at time of the
> unclean shutdown.  I know EXT2/EXT3 correctly honor the 'sync' flag,
> which if used should reduce (but not eliminate) your chances of
> filesystem corruption by an order of magnitude.  The only time your
> filesystem is vulnerable to corruption on unclean shutdown is when a
> process is writing to a file.

The general purpose journaling file systems (Reiserfs/ext3/xfs) are very
heavy on writes to the media [1] - which is a pig for flash. If you go
this way your flash media may wear out a lot more quickly than you'd
expect.

> You may also have complications with Linux in that you may not just
> arbitrarily unplug the USB device from a running system where it has
> been mounted.  It first has to be unmounted from software before
> being unplugged.
>
> //Jesse Off
>

Jim

[1] I believe on ext3 there are at least 3 writes to what would be 1 ext2
write - one to write the journal entry, one to update the actually file,
then the deletion of the journal entry.



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