Re: The danger of dishonest disk drives (WAS:Re: Need to remove a ghost file, but can't because it doesn't exist)
On Thu, Nov 23, 2006 at 04:37:15PM -0500, hendrik@topoi.pooq.com wrote:
> On Thu, Nov 23, 2006 at 02:25:57PM -0500, Douglas Tutty wrote:
> >
> > Note that IBM does say that jfs focus more on being able to restore
> > filesystem integrity than on data integrity. For higher integrity they
> > suggest the sync mount option.
>
> reiser4 is *supposed* to care about data integrity as well. But it's
> still not in a stable release according to its developer (last time I
> looked) and he seems to be in jail at the moment.
>
Hi Hendrik
Its not that JFS doesn't care about data integrity it just that, given
the choice to being able to mount a file system with some loss of data
or not being able to mount it after fixing and leaving the data
somewhere on the disk, JFS choses the former. If it chose the latter,
then it would have to say something like "The file system is FUBAR and
you need to use alternate methods to retreive your data off this drive".
IBM would rather have the server come back up and carry on running, then
the sysadmin can restore a file from backups.
Since I haven't run into this problem, I don't know what types of error
messages it says, like "File system integrety has been restored, however,
some data has been lost from files x,y,z". I have had FUBARed ext3 and
reiserfs partitions.
The question is how does the file system know that a write has made it
to disk. E.g. if the file system is atomic transaction oriented, how
can the file system know that a commit has been committed if the drive
lies?
Doug.
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