Re: Data Offset

[Phil Turmel <philip@turmel.org>]

On 06/13/2012 05:46 AM, Pierre Beck wrote:

[trim /]

> And DON'T run fsck early. Try mounting read-only, take a look at your
> data. Something bigger than chunksize, like a movie file, checksum some
> iso or smth. It should be intact. THEN run fsck. fsck cannot expect raid
> stripe reordering and worst case may cause damage (not that I heard of
> it happen, but inspecting data first is safe).

This is *dangerous* advice.  Modern filesystems will replay their
journal even when mounted read-only.  When attempting to determine the
member order, mounting the file system is *not* safe.  And some
filesystems ignore the read-only status of the array, so that won't
avoid the problem.

fsck -n is the *only* safe way to automate the check.  Hex dumps of
expected signature blocks is even better, but is difficult to automate.

HTH,

Phil