batches and serial numbers (was "Re: md vs LVM and VMs and ...")

[David T-G <davidtg-robot@justpickone.org>]

Anthony, et al --

...and then Wols Lists said...
% On 03/12/2022 05:41, David T-G wrote:
% > 
% > The good news here is that I don't mix disk sizes; all of these are not
% > only the same size but, for the foreseeable future, the exact same model.
% 
% From the exact same batch? That's BAD news actually.

I don't know about the same batch.  I got three together, so maybe, and
then I recently added a fourth.

  diskfarm:~ # for D in /dev/sd[bcdk] ; do printf "$D\t" ; smartctl -i $D | grep Serial ; done
  /dev/sdb        Serial Number:    61U0A0HQFBKG
  /dev/sdc        Serial Number:    61U0A0BEFBKG
  /dev/sdd        Serial Number:    61U0A007FBKG
  /dev/sdk        Serial Number:    91C0A03ZFBKG

How close is too close for SNs?  Anyone have a magic decoder ring?

I seriously think I'm going to be asking for another -- plus the
corresponding offsite external drive -- for Christmas, so we'll be
even more homogeneous as time goes on and maybe sooner than later.


% 
% Now that disk sizes have been standardised (and the number of actual
% factories/manufacturers seriously reduced), it should be that a 1TB drive is
% a 1TB drive is a 1TB drive. Decimal, that is, not binary. So there
% *shouldn't* be any problems swapping one random drive out for another.

That would be nice.  But it just feels so ... WRONG! :-)  I don't want
to have to sweat different numbers of sectors or different caches or
different speeds that will just make hiccups.  I'm not yet sold on
going multi-vendor all together ...  [In different arrays or machines,
certainly, but not when they're supposed to be identical members.]


% 
% But if all your drives are the same make, model(, and batch), there is a not
% insignificant risk they will all share the same defects, and fail at the
% same time. It's accepted the risk is small, but it's there.

What is the problem?  Is it the manufacturer's firmware?  Is it the day
they were made?  If I order a Tosh, a Seag, and a WD all on the same day
then it sounds like I'm [much more] likely to get clones made at the same
time in those few factories.  But I couldn't just buy a drive a quarter
and wait nearly a year to get up and running; I had to start somewhere ...


% 
% It's why my raid is composed of a Seagate Barracuda 3TB (slap wrist, don't
% use Barracudas!), 2 x 4TB Seagate Ironwolves, and 1 Toshiba 8TB N300.

These are Tosh X300s, FWIW.  Like 'em so far!


% 
% Cheers,
% Wol


HAND

:-D
-- 
David T-G
See http://justpickone.org/davidtg/email/
See http://justpickone.org/davidtg/tofu.txt