linux-kernel - Re: Filesystem for block devices using flash storage?

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Message-ID: <20081011185157.478ea357@lxorguk.ukuu.org.uk>
Date:	Sat, 11 Oct 2008 18:51:57 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Pavel Machek <pavel@...e.cz>
Cc:	Chris Snook <csnook@...hat.com>,
	Stefan Monnier <monnier@....umontreal.ca>,
	linux-kernel@...r.kernel.org
Subject: Re: Filesystem for block devices using flash storage?

> > Writes to magnetic disks are functionally atomic at the sector level.

No they are not.

> I don't think ext3 is safe w.r.t. whole eraseblocks disappearing. So
> if you write data 'nearby' root directory and power fails, bye bye
> filesystem, and journal will not help.

You have similar problems on rotating media. A write to a block can
corrupt other blocks adjacent to the block you write, and on the latest
disks the physical block size can be greater than the logical one so
unless you laid your partitions out right you have read-modify-write
cycles goin on.

Alan
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