:: Re: [DNG] Can this drive be saved?
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Author: Mason Loring Bliss
To: Hendrik Boom
CC: dng
Subject: Re: [DNG] Can this drive be saved?
On Sat, Sep 05, 2020 at 01:41:46PM -0400, Hendrik Boom wrote:

> Nowadays the hardware replaces individual bad blocks without bothering
> the file system.

Where it can, yeah. That said, I've seen some of the corruption that we're
supposed to never see - the bitflips in files that people use to
demonstrate self-healing filesystems - prior to my become a ZFS zealot.

The awfully nice thing about ZFS is that if you have a mirror or better,
each drive stores both data and a checksum of that data, so you have an
awfully good chance of finding one bit of recorded data that matches one
checksum, and if you have that, ZFS can rewrite all the bad data. Even with
a single disk, you can specify multiple copies to achieve the same thing,
although catastrophic failure of the disk is always a possibility, making a
proper mirror *and* back-ups preferable.

As a random note, the upstream ZFS custom package instructions work out of
the box on Devuan, and they still ship sysvinit files when built that way.


At some point there will be other filesystems that do the same. BtrFS isn't
far behind, and hopefully some increased attention will get it the rest of
the way. Red Hat's Stratis and DragonflyBSD's Hammer2 will both have self-
healing working before long, using different approaches.

Mason Loring Bliss (( If I have not seen as far as others, it is because
mason@??? )) giants were standing on my shoulders. - Hal Abelson