Re: [PLUG] RAID6 or RAID5+HS?

[Rich Freeman <r-plug@thefreemanclan.net>]

On Mon, Aug 22, 2016 at 12:57 PM, Keith C. Perry
<kperry@daotechnologies.com> wrote:
>
> What was on my mind was this...  Lets not go crazy of the new shiny
> thing.  Yes ZFS (and BTRFS) have more mechanisms to protection their
> file systems from failures.  That conversation usually leads to
> something about random bits flipped to which I say, if you are worried
> about that then run systems with ECC RAM because any bit flip anywhere
> will lead to data corruption somewhere.  In other words, use the right
> tool for the job (when you can).

I mostly agree, but I just wanted to say that lack of ECC isn't really
a reason to prefer something less robust.  You have more security with
non-ECC+btrfs/zfs than non-ECC+ext4.

The other factor is that picking a filesystem is purely a matter of
software.  Having ECC RAM requires a supporting
northbridge/motherboard.  If you're going the AMD route it is often
available "for free" other than the extra cost on the RAM itself.  You
just have to check motherboard compatibility (which often isn't
well-documented).  If you're going the Intel route it means buying an
i7 or Xeon, and that is anything but free unless you were already
planning on buying one.  Intel disables ECC support on the i5 and
lower CPUs (just another reason we should all be praying that AMD
comes out with a decent next generation, whether you intend to ever
buy an AMD chip or not).

However, when I buy my next server CPU I do actually plan to take a
look at ECC.  I actually had a windows desktop drive hosed by a RAM
corruption recently.  It was a pain but the system didn't really house
anything critical

>
> My point from there is that ZFS and BTRFS do NOT mean you don't run backups.

No argument there, though both filesystems offer a much more
streamlined solution for backups.  (Though I'm not inclined to trust
it so much for btrfs.)  And as you point out some data may not require
backup.

RAID helps avoid downtime in the event of hard drive hardware failure.
That is a common failure mode worth protecting against, but it isn't
the only one out there.  Backups protect against many other failure
modes, but they almost always involve substantial downtime when you
need to rely on them.  I'd look at RAID as a way to change the oil on
your car without turning it off.  It doesn't eliminate the need for
other preventative maintenance, but you know you'll need oil changes,
and so it doesn't hurt to be able to do it on the run.

-- 
Rich
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