[NCLUG] sw raid, recovery after install

[Michael Milligan]

On 01/16/2013 04:36 PM, Stephen Warren wrote:
> On 01/16/2013 04:07 PM, Michael Milligan wrote:
> 
>> https://bugs.launchpad.net/ubuntu/+source/mdcfg/+bug/77470
> 
> Ugggh. I sincerely hope that never gets fixed, or e.g. RAID-1 array
> scrubbing never has a chance of finding that the mirrors are in sync...

But who cares if there's no useful data on the drives to begin with?
(which is the case when doing an install.)  When you do the mkfs (or it
happens via the installer), everything you care about gets mirrored
properly at that point.  And a bit later on you aren't sitting there
twiddling your thumbs waiting for packages to expand on an array that is
busy copying blocks back and forth between drives slowing down your
install making it take much longer than it should.  It's painful.  And
in my case, I have better things to be doing with my time.

When a reconstruct next happens (or checkarray runs on a Debian system),
WELL AFTER your install is done, all those blocks you dan't care about
will get silently "fixed".  Late at night, while you are either sleeping
or doing something else productive.  ;-)

RAID is a block-level thing, ignorant of the file system on top of it.
If you take into consideration the data you actually care about (which
is nothing at the start of an install), this hopefully makes sense and
saves a LOT of time on an install.

Or to put it another way, do you really care if the garbage on one drive
is synced to the other mirror prior to over-writing all that garbage
with a new file system and files?

Regards,
Mike

PS:  "zpool scrub <pool>" rocks instead and is NOT silent about sync errors.