How to speed up slow zpool scrub?

[Bob Friesenhahn]

On Wed, 27 Apr 2016, Michael B. Eichorn wrote:
>
> It does not *need* to be ECC ram, ECC is just *highly recommended*. As
> one of the key features of zfs is bitrot prevention, it makes sense to
> protect against bitrot everywhere. Zfs (and thus freenas) is just fine
> with non-ecc ram. Just, like for any filesystem if the bit is flipped
> in ram it will be recorded as such on disk.

This is not necessarily the case.  Zfs does not offer additional 
protections for data in RAM.  It assumes that data in RAM is protected 
in other ways.  The on-disk checksum only verifies that the data was 
not modified since it was checksummed, but it may already be corrupt. 
The risk factor is pretty high if RAM becomes corrupted since zfs uses 
so much RAM.

It is possible to lose data and even the whole pool due to memory 
corruption.

There are well known cases where users encountered continual/periodic 
pool corruptions due to flaky RAM.

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