zfs scrub enable by default

[Alan Somers]

On Wed, Aug 5, 2020 at 7:15 AM Bob Friesenhahn <bfriesen at simple.dallas.tx.us>
wrote:

> On Tue, 4 Aug 2020, Karl Denninger wrote:
>
> > Let me give you two allegedly "degenerate" cases that are actually not
> > degenerate at all.
> >
> > 1. A laptop or workstation.  It is backed up.  It uses ZFS because it's
> > faster, and I can establish a filesystem for some project very easily
> and
> > quickly, it's segregated, I can work on it and destroy it trivially when
> > done.  I can set quotas on that, etc.  If I want to move its mountpoint,
> I
> > can trivially do so. And so on.  Note that here there is no redundancy
> at
> > all; no raidZx, no mirroring, etc.  I'm merely using it for convenience.
>
> Did you remember to set copies=2 or copies=3 for zfs filesystems where
> you hope not to experience data loss?  It needs to be set as soon as
> possible since it only applies to new files.  This is a way to get
> more media redundancy, although the whole drive may fail.
>
> Zfs scrub is not going to protect your precious data from loss given
> just one drive unless you increase the copies setting.  Zfs itself
> already uses redundant copies for its own data structures.
>

-1.  In my experience, based on many thousands of drives, a whole drive
failure is more likely than the failure or silent corruption of a few
sectors.  The ZFS copies setting really isn't very useful with modern HDDs.
-Alan