[TriLUG] Disk drive recovery services

[David Burton via TriLUG]

I see that there was a class-action lawsuit over the ST3000DM001:
https://www.extremetech.com/extreme/222267-seagate-faces-lawsuit-over-3tb-hard-drive-failure-rates
Wow, what a disaster!

It used to be that hardware RAID demanded identical drives. So a typical
RAID array would have a batch of brand new drives, often all made the same
day, in the same factory, perhaps even with consecutive serial numbers.

Then, of course, as part of the same RAID array, the drives would have
nearly-identical usage patterns.

And then people would be shocked when two or three of the drives all failed
on the same day, resulting in data loss.

Fortunately, Linux Software RAID doesn't require identical drives. The
chance of simultaneous failures drops tremendously if the drives are
different makes & models.

Also fortunately, I don't need massive amounts of storage. So my little 2TB
home server contains *three* cheap 2TB drives, using Linux software RAID1
mirroring. That is, it's doubly mirrored, *and* I used two different brands
of drives. (Two of the drives are the same make & model, but their
manufactured dates are a couple of months apart.)

I do not worry about drive failures on my server!

A bonus is that, at least if you're using spinning rust, Linux speeds up a
lot when you feed it RAID1 mirrored drives. (My server is so lightly loaded
that that doesn't really matter, to me.)

One thing I've wondered about is what performance is like with Linux RAID1
SSDs. My guess is that they're so fast that mirroring them doesn't speed up
Linux. But what about mixing drive types? I'm imagining a RAID 1 array with
an SSD mirrored by one or two HDDs. I assume it'll work, but how's the
performance? Has anyone tried it?

Dave


On Tue, Sep 22, 2020 at 6:51 PM Joseph Mack NA3T via TriLUG <
trilug at trilug.org> wrote:

> On Tue, 22 Sep 2020, Wes Garrison via TriLUG wrote:
>
> Hi Wes,
>
> > It wasn't the fault of ZFS.
>
> ah.
>
> > I was using the notorious Seagate ST3000DM001, which is a consumer drive
> not
> > meant for NAS (not meant for much of anything really).
>
> OK
>
> > Out of the original 8, only 2 remain.  Worst failure rate I've ever seen.
>
> :-(
>
> > I was using a ZFS Z2 array (which can support 2 simultaneous failures),
> and
> > had 3 simultaneous failures; the latter 2 occurring during re-silvering.
> This
> > is pretty common, apparently.  When you have a failure and start
> hammering the
> > drives to do a rebuild, you often have more failures.
>
> Jim Salter (gave us a talk about 2 years ago), says to only use mirrors to
> avoid
> rebuild problems. Here's why you shouldn't RAID anymore (anymore started
> in
> 2015). Instead just mirror.
>
> https://jrs-s.net/2015/02/06/zfs-you-should-use-mirror-vdevs-not-raidz/
>
> Also it seems crazy, now that he points it out, to have to access 5 drives
> (or
> whatever) to get your read or your write.
>
> > Lessons learned:
> > 1) Use NAS drives or Seagate Exos for RAID/ZFS arrays, not crappy
> consumer
> > drives.  If you buy WD, make sure you get CMR and don't get fleeced with
> > SMR drives.
>
> yup.
>
> > 2) use ZFS Z3 for better fault tolerance
>
> Jim says to mirror. After reading his article, I'm convinced.
>
> > 3) have an actual backup if practicable.  This is hard when your array
> is
> > huge.  How do you back up an 18TB array when the largest available
> consumer
> > drive is 4TB?  With another 18TB array, of course!
>
> That's how we did it when we had 10MB drives too.
>
> Thanks Joe
>
> --
> Joseph Mack NA3T EME(B,D), FM05lw North Carolina
> jmack (at) wm7d (dot) net - azimuthal equidistant
> map generator at http://www.wm7d.net/azproj.shtml
> Homepage http://www.austintek.com/ It's GNU/Linux!
> --
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