In message 
          bob prohaska  wrote:

> Martin Gregorie  wrote:
> > On Sun, 13 Dec 2020 16:38:29 +0000, bob prohaska wrote:
> >
> > > I attribute the acceptable performance to the drive being new, with 1
> > > TB capacity. Once it starts re-writing old sectors it'll likely slow
> > > much more.
> > >
> > AFAIK trim isn't supposed to do anything useful to a hard drive
> > regardless of speed or capacity, but I know nothing about SMR, except
> > that an article I just read says its really only suitable for large
> > scale  data storage with minimal updating, i.e. not something I'd use
> > for the  (main? only?) storage volume for a Linux or Windows system and
> > definitely  not for a journalled fling system.
> >
> Practically, SMR is not readily avoidable. It's denser and therefore
> cheaper than conventional perpendicular recording and has found its way,
> unbidden, to a wide range of sizes, speeds and brands. The drawback is
> that, like flash, data is written in relatively large blocks. Writes to an
> entirely unused  block proceed without a delay. Changes to an
> already-written block require it be copied, edited and re-written in much
> the same fashion as flash, absent the write fatigue problems of flash. Trim
> functions on an SMR drive much as it does on a flash device, preemptively
> preparing new, empty blocks for prompt use by consolidating partly-used
> blocks accumulated during earlier writes.
>
> When something triggers a long period of sustained writes, like
> reconstructing a raid array, this overwhelms the preparatory consolidation
> and slows writes to a crawl. It's not that it doesn't work, rather that it
> works badly.
>
> I should emphasize that this summary is my own interpretation of a random
> selection of Internet research, and is therefore entirely suspect......

I've drawn the same conclusions as you, from what I've read.  With one
small exception: I believe that, if you dig deeply enough into the
manufacturer's specification, you can see whether a particular drive
uses SMR, and therefore avoid it if you so wish.

David

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