Re: ext4 features

[Chuck Ebbert]

In-Reply-To: <20060707195223.GA12301@xxxxxxxxx>

On Fri, 7 Jul 2006 15:52:23 -0400, Theodore Tso wrote:

> Not four times a day, but probably once a month or two it would be a
> *very* good idea to do periodic sweeps of files to make sure the hard
> drive hasn't corrupted the files out from under you.  If you have 20+
> TB of data, the probability of silent data corruption starts going up.
> That would be justification for storing the checksum in the inode or
> in the EA of the file, with the kernel automatically clearing it if
> the file was *deliberately* changed.  The goal is to detect the disk
> silently changing the data for you, free of charge....

Per-extent checksums on ext4 might work better.

        -  If you only changed a small part of a file the majority of
           checksums would still be valid.

        -  On a file with 31K of data in a 128K extent, checksumming
           the wasted space might cause false positives but it would be
           OK because that would still be actual on-disk corruption.

-- 
Chuck
 "You can't read a newspaper if you can't read."  --George W. Bush
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