Jerky video playback

[Volker Wysk]

Am Mittwoch, dem 14.06.2023 um 16:29 +0200 schrieb Ralf Mardorf via ubuntu-
users:
> On Wed, 2023-06-14 at 16:06 +0200, Volker Wysk wrote:
> > Am Mittwoch, dem 14.06.2023 um 15:42 +0200 schrieb Ralf Mardorf via ubuntu-
> > users:
> > > On Wed, 2023-06-14 at 15:01 +0200, Volker Wysk wrote:
> > > > There's another strange thing, which might or might not be related. I have
> > > > two external hard disks, which I use for backups. Both have USB 3. When I
> > > > synchronize the two, I get a data transfer rate which fluctuates between
> > > > about 20 MB/s and 150 MB/s. That's what's displayed by the "rsync" command.
> > > > I expect that this display is smoothed.
> > > 
> > > from hearsay it's what I would expect from shingled magnetic recording
> > > (SMR) drives, see picture: 
> > > https://www.researchgate.net/figure/Real-time-bandwidth-of-SMR-vs-CMR-disks-when-performing-random-writes_fig1_339923370
> > > For visually impaired subscribers a description of the real-time
> > > bandwidth of SMR vs. CMR disks when performing random writes. For CMR
> > > drives it's more or less a flat line, while for SMR drives read:
> > > https://www.musixmatch.com/lyrics/Vengaboys/Up-Down
> > 
> > That last link points to some music lyrics... You've posted the wrong link,
> > have you?
> 
> No, it's just a joke. Bandwidth up and down and up and down ...

Okay.  :-)

> > I get the idea, what this shingled magnetic recording is (see Wikipedia).
> > But I DON'T have many random writes. Most data is in a dozen or so of very
> > large dar archives.
> > 
> > If it IS because of that SMR, then it's a weakness of the technology, not a
> > (hardware) error, right?
> 
> Correct, that's my guess.
> 
> Even when syncing large files, it's a sync between two drives that
> aren't empty, hence I would assume the worst. The drives aren't just
> writing the new large files, they are also reading and rewriting several
> layers of data of the same size the new files have got.

I see...

> As long as I can get inexpensive CMR disks for backups I buy those. 

Yeah, I start my backup (and a following "systemctl poweroff") when I go to
bed. So it doesn't matter how fast it is.

> A
> dedicated Toshiba series I often bought is migrating from CMR to SMR. My
> dealer already sells some sizes as SMR only, while some other sizes are
> still available as CMR, but in limited numbers.
> 
> What I will buy as soon as all inexpensive drives are SMR drives, will
> depend on my financial situation.

Bye,
Volker
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