zfs scrub enable by default

[Bob Friesenhahn]

On Wed, 5 Aug 2020, Alan Somers wrote:
>>
>> 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.

This is something that I totally agree with.

In this case a scrub will not help all that much other than make your 
'bad day' occur earlier if the scrub pushes the device over the brink 
due to the increased loading.

Scrub is more likely to successfully correct issues given sufficient 
physical redundancy but finding the issues right away is less 
important given sufficient physical redundancy since issues will be 
automatically corrected upon data access.

Manual scrub of a new pool (after copying in the data) is a very wise 
idea in order to uncover system-level issues.

Bob
-- 
Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/
Public Key,     http://www.simplesystems.org/users/bfriesen/public-key.txt