Re: [gentoo-user] [OT] SMR drives (WAS: cryptsetup close and device in use when it is not)

[Frank Steinmetzger]

Am Thu, Jul 29, 2021 at 05:46:16PM +0100 schrieb Wols Lists:

> > Yea. First the SMR fiasco became public and then there was some other PR
> > stunt they did that I can’t remember right now, and I said “I can’t buy WD
> > anymore”. But there is no real alternative these days. And CMR drives are
> > becoming ever rarer, especially in the 2.5″ realm. Except for one single
> > seagate model, there isn’t even a bare SATA drive above 2 TB available on
> > the market! Everything above that size is external USB stuff. And those
> > disks don’t come with standard SATA connectors anymore, but have the USB
> > socket soldered onto their PCB.
> >
> Are you talking 2.5" drives here?

I meant in general, but – as I said – “especially in the 2.5″ realm”. ;-)
For 3.5″, it’s mostly the low-capacity drives that are affected. Probably
because here the ratio of fixed cost (case, electronics) vs. per-capacity
cost (platters, heads) is higher, so the pressure to reduce manufacturing
cost is also higher. High-capacity drives tend to remain CMR at the mo’.

> The SMR stunt was a real cock-up as far as raid was concerned - they
> moved their WD Red "ideal for raid and NAS" drives over to SMR and
> promptly started killing raid arrays left right and centre as people
> replaced drives ... you now need Red Pro so the advice for raid is just
> "Avoid WD".

Red Plus is fine, too. I think the “Plus” is marketing speak for non-SMR.
Which is why probably SMRs now have the price tag of old CMRs, and the new
CMRs have a “plus” on the price tag.

> From what I can make out with Seagate, the old Barracuda line is pretty
> much all CMR, they had just started making some of them SMR when the
> brown stuff hit the rotating blades.

Seagate made a statement that their NAS drives are not and never will be SMR.



In case someone is interested, here’s a little experience report:

Two days ago, I bought a 2.5″ WD My Passport 4 TB for a new off-site backup
strategy I want to implement. They even killed the rubber feet on the
underside to save a few cents. >:'-( ) Interestingly, the even cheaper
elements series (which is the cheapest because it has no complimentary
sofware and no encryption or password feature) still has them. Probably
because its case design is older.

I just finished transferring my existing Borg backup repos. Right at the
beginning, I tested a small repo of 3 GiB and I got good throughput. After
around 2 GiB or so the drive went down to 10 MiB/s for a very long time
(writing at least another 3 GiB, I have no idea what that was).

I was already pondering my options. But once that was over, I’ve since been
writing 1,2 TiB to the drive with rsync happily without any glitches,
averaging at slightly above 100 MiB/s. I used SMR-friendly ext4 settings and
Borg uses datafiles of 500 MiB size, which greatly reduces sprinkled
metadata writes b/c it’s only a few thousand files instead of millions.

According to smartctl, the drive claims to support Trim, but so far I’ve
been unsuccessful to invoke it with fstrim. First I had to enable the
allow-discard option in the underlying LUKS container, which is disabled by
default for security reasons. But either I’m still missing a detail, or the
USB-SATA-bridge really does not support it. Or it does, but the kernel is
unaware: yesterday I read an article about enabling a flag for the USB
controller via a custom UDEV rule. Who knows.

-- 
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