I'm looking for an HDD in the 2-4TB range as the data drive for a PC
(boots off SSD, but I'm not paying SSD prices for 2TB+).

I see that the market is still divided between SMR ('shingled' magnetic
recording) and CMR/PMR ('Conventional'/'Perpendicular') models, with
the CMR drives being almost unobtainable.

SMR drives write overlapping tracks to maximize the use of the area of
the platter, but to do this they have to write tracks in groups, and if
a sector in a group has to be updated it is necessary to rewrite that
sector AND any that overlap it, which increases the time taken, and
also the wear on the heads and stepper assemblies.

I recall there was a lot of fuss, a few years ago, about SMR drives
performing significantly less efficiently at random writes --
unsurprising, considering the technology, and something that will
happen quite a lot on a drive used for general data storage on a PC
used for software development -- and so I've been avoiding them. There
was even more fuss when it emerged that some manufacturers (maybe all
of them) were replacing CMR models with SMR ones without telling
anyone. Nowadays you can tell one from the other if you can find enough
small print to read, but it sometimes isn't easy.

I ordered a 3TB Toshiba HDWD130UZSVA which is supposed to be a CMR
drive, but it was DOA, and the supplier, while happy to replace it, has
no more stock and can't give a timescale for availability. I can wait a
while, but the dead disk was manufacturer early in 2022, and I'm afraid
that if I wait for a new Toshiba 3TB drive I'll find when I get it that
the model has been replaced by an SMR design.

The other drives they stock at that sort of size all seem to be SMR,
apart from the WD Black drives which are significantly more expensive.

So, my question is: Am I right still to be avoiding SMR drives, or have
they become better since they were introduced. I see that SMR drives
tend to have larger caches than CMR, and some support TRIM, which
rather suggests that the onboard controllers are using some of the same
write-optimization techniques as are used on SSDs.

What does the team think? Is there still a noticeable reduction in
performance with SMR drives for general/development work, or are they
now OK?

--
Cheers,
Daniel.

On 25/06/2023 in message <VA.00000db2.001d75a0@me.invalid> Daniel James
wrote:

>I'm looking for an HDD in the 2-4TB range as the data drive for a PC
>(boots off SSD, but I'm not paying SSD prices for 2TB+).

Prices have dropped enormously, you can get 4 TB for around £200 nowadays.

--
Jeff Gaines Dorset UK
Greater love hath no man than this, that he lay down his friends for his
life.
(Jeremy Thorpe, 1962)

Daniel James <daniel@me.invalid> writes:
> What does the team think? Is there still a noticeable reduction in
> performance with SMR drives for general/development work, or are they
> now OK?

On the suitability of SMR for your use case, no idea.

But a few general thoughts:

- Unless one is doing an awful lot of bulk or synchronous writes (for
bulk: enough to persistently saturate buffers in RAM and device), the
higher latency predicted for SMR writes shouldn’t be very visible -
applications will get on with real work while writes complete in the
background.

- If one isn’t writing such large quantities of data on the regular that
a 3TB medium is really required then then maybe an SSD sized for the
OS and working set, plus a slower disk for rarely-modified bulk data
where SMR’s issues are unlikely to be as relevant, would be more
appropriate.

- It’s worth considering whether the cost savings of a PMR disk are
worth the time spent finding one compared to just buying a big SSD.
(I did the latter although there are also space constraints in my use
case meaning I wanted a single device.)

--
https://www.greenend.org.uk/rjk/

Jeff Gaines <jgnewsid@outlook.com> wrote:
> On 25/06/2023 in message <VA.00000db2.001d75a0@me.invalid> Daniel James
> wrote:
>
> >I'm looking for an HDD in the 2-4TB range as the data drive for a PC
> >(boots off SSD, but I'm not paying SSD prices for 2TB+).
>
> Prices have dropped enormously, you can get 4 TB for around £200 nowadays.

Yes:

Cheapest 4TB HDD: £73.99 (Toshiba HDWD240UZSVA SMR)
Cheapest 4TB 2.5" SATA: £196.99 (Samsung 870 QVO)
Cheapest 4TB M.2 NVMe: £79.98x2=£159.96 (Intel 670p 2TB twice)

(if you don't have two spare M.2 slots, passive adapters to PCIe slots are a
few pounds)

Prices from Scan, who are by no means the cheapest but easy to look up
(they're also my go-to for business orders)

If you can't stretch to 4TB NVMe at the moment, maybe buy 2TB now and 2TB
later when the drive fills up, when it will likely be cheaper still.

Theo

On 25/06/2023 13:21, Theo wrote:
> Cheapest 4TB HDD: £73.99 (Toshiba HDWD240UZSVA SMR)
> Cheapest 4TB 2.5" SATA: £196.99 (Samsung 870 QVO)
> Cheapest 4TB M.2 NVMe: £79.98x2=£159.96 (Intel 670p 2TB twice)

Thanks, Theo, and others.

Yes, I had done that piece of homework. There's also:

Not-so-cheap 4TB CMR HDD £126.49 (Toshiba Enterprise MG04ACA400E)

(Scan, again. They're the dealer I was using anyway)

That's kind-of tempting in that it allows me to keep the same storage
configuration that I had before (/ on 120GB SSD, /home on big HDD) and
is only two-and-a-bit times as expensive as my first choice while giving
33% more storage. Not a bargain, but it avoids SMR without going all-SSD
which would require a change of plan as well a higher cost.

The best alternative to that, for me, is to get a big 2.5" SATA SSD, as
you say, and put the whole filesystem on that. That's also tempting, for
different reasons.

(I'm not going the NVMe route as I change the drives around often enough
that I have them in removable bays to avoid the faff of opening the case
up. I have seen M.2 removable-drive bays, but they were SATA-only, so
nothing really to gain over 2.5" jobs.)

However, this doesn't answer my original question, which is piquing my
curiosity more and more, which is whether SMR drives have got any better
-- or, rather, have they improved enough -- now that they have bigger
cache and controllers that clearly remap sectors to minimize rewriting.
Does anyone know? Anyone seen a review?

--
Cheers,
Daniel.
--
Cheers,
Daniel.

On 25 Jun 2023 at 17:39:41 BST, "Daniel James" <daniel@me.invalid>
wrote:

> However, this doesn't answer my original question, which is piquing my
> curiosity more and more, which is whether SMR drives have got any better
> -- or, rather, have they improved enough -- now that they have bigger
> cache and controllers that clearly remap sectors to minimize rewriting.
> Does anyone know? Anyone seen a review?

They were, in fact, always fine for most purposes in a domestic PC. The
amount of cache around hides the issues almost all the time because
domestic PC use doesn't stress the caches.

The primary thing they're troublesome for is using in RAID
configurations, where rebuilding the RAID after a drive swap (consisting
of writing data across the entire new drive, both sequentially and
randomly as well unless you rebuild offline) can take longer than the
expected time between hdd failures in the rest of the RAID... which is
obviously a problem.

After the debacle of WD selling NAS-labelled SMR drives in 2020 or so,
they now declare themselves.

https://www.seagate.com/gb/en/products/cmr-smr-list/
https://support-en.wd.com/app/answers/detailweb/a_id/50697/~/determine-if-an-internal-drive-uses-cmr-or-smr-technology

Back at the time, the clear answer was "get a >4TB HDD, it'll be CMR":
https://www.tomshardware.com/news/wd-lists-all-drives-slower-smr-techNOLOGY

which was true then but may not be now. Larger drives do have other
benefits, of course - faster data transmission as well as capacity.

Do note that a drive that *doesn't* specify could be either SMR or CMR
but is very likely to be CMR. Don't pay double just because the shop
page says CMR; for the price of that 4TB one you note you could easily
get an 8TB CMR. And almost a 4TB SSD...

Cheers - Jaimie
--
"If you can't make fun of it, it's probably not worth taking seriously"
-- http://survivingtheworld.net/Lesson494.html

On 25/06/2023 18:28, Jaimie Vandenbergh wrote:
>> ... whether SMR drives have got any better -- or, rather, have
>> they improved enough -- now that they have bigger cache and
>> controllers that clearly remap sectors to minimize rewriting.
>
> They were, in fact, always fine for most purposes in a domestic PC.
> The amount of cache around hides the issues almost all the time
> because domestic PC use doesn't stress the caches.

Thanks for that insight, Jaimie.

Yes, for most domestic PCs (and for mine, much of the time) that's
certainly true. However I do know that some of the things I regularly
(though not frequently) do ARE likely to stress the caches. Most SMR
drives seem to have about 4 times the cache of a similar-sized CMR
drive, and this may be enough to avoid any problems -- I don't know,
which is why I'm after some real-world data.

I do appreciate that I am probably looking into this more deeply than I
need ...

> The primary thing they're troublesome for is using in RAID
> configurations ...
Yes, though why rebuilding a RAID array can't be done in such a way that
the writes are all sequential is a bit of a puzzle ... perhaps the issue
arises because the array is in use while it is rebuilding ...?

ZFS also gets a mention as having problems with SMR.

> After the debacle of WD selling NAS-labelled SMR drives in 2020 or
> so, they now declare themselves.
Most of the manufacturers seem to do so ... if you look hard enough at
the spec sheets and read enough small print. The only data sheets I've
come across recently that make no mention at all of SMR are dated around
2015 or so, and so probably predate the problem!

> Back at the time, the clear answer was "get a >4TB HDD, it'll be
> CMR":
If anything, it's the larger drives that seem more likely to be SMR,
these days, except for 'enterprise grade' drives and NAS drives which
tend to be CMR (for a reason) and more expensive. A good rule of thumb
seems to be that if it has 64MB cache it's probably CMR and if it has
256MB it's probably SMR (though larger/faster drives tend to have more
cache than smaller/slower/cheaper ones).

> Do note that a drive that *doesn't* specify could be either SMR or
> CMR but is very likely to be CMR. Don't pay double just because the
> shop page says CMR
Indeed. Always go by the data sheets, and try to understand what you're
getting for the money. I know that.

--
Cheers,
Daniel.

On 6/25/23 13:21, Theo wrote:
> Jeff Gaines <jgnewsid@outlook.com> wrote:
>> On 25/06/2023 in message <VA.00000db2.001d75a0@me.invalid> Daniel James
>> wrote:
>>
>>> I'm looking for an HDD in the 2-4TB range as the data drive for a PC
>>> (boots off SSD, but I'm not paying SSD prices for 2TB+).
>>
>> Prices have dropped enormously, you can get 4 TB for around £200 nowadays.
>
> Yes:
>
> Cheapest 4TB HDD: £73.99 (Toshiba HDWD240UZSVA SMR)
> Cheapest 4TB 2.5" SATA: £196.99 (Samsung 870 QVO)
> Cheapest 4TB M.2 NVMe: £79.98x2=£159.96 (Intel 670p 2TB twice)
>

> (if you don't have two spare M.2 slots, passive adapters to PCIe slots are a
> few pounds)
>
> Prices from Scan, who are by no means the cheapest but easy to look up
> (they're also my go-to for business orders)
>
> If you can't stretch to 4TB NVMe at the moment, maybe buy 2TB now and 2TB
> later when the drive fills up, when it will likely be cheaper still.
>
> Theo