Re: Performance variation in traditional HDDs?

Here's another CMR drive (https://pcpartpicker.com/product/6FQcCJ).
Here, two identical drives with same model number and firmware show
about a 10% difference in performance.

Looking at the average full drive write speed we saw the following
results in MB/s:

Drive 1: 153.86, 153.86, 153.86
Drive 2: 140.63, 140.64, 140.65

Again, each individual drive is incredibly consistent in its
performance. But drive 1 is over 9% faster than drive 2. And the
graphs of bandwidth over time for a full write are markedly different:

https://cdna.pcpartpicker.com/static/forever/images/content/684ce1fea2858681575fb7666b8b987f.png

Reporting benchmarked performance for HDDs is problematic when there
is variation like this between two of the same drive.

On Sun, Apr 27, 2025 at 12:23 PM Nick Neumann <[email protected]> wrote:
>
> On Wed, Apr 23, 2025 at 10:00 PM Damien Le Moal <[email protected]> wrote:
> > So these are drive-managed SMR disks, right ?
>
> Yes. I chose these first because they show the largest performance
> difference between two "identical" drives. We do an ATA SECURITY ERASE
> to reset their state/LBA mapping - it takes longer than a full drive
> write.
>
> Here is another set of identical drives
> (https://pcpartpicker.com/product/XtjG3C) that just completed and also
> show a significant performance difference. These are CMR drives with
> the same model number and firmware.
>
> We did three full drive writes on each drive, using the same proper
> horizontal mounting and position.
>
> Looking at the average full drive write speed we saw the following
> results in MB/s:
>
> Drive 1: 162.72, 162.73, 162.73
> Drive 2: 155.69, 155.70, 155.72
>
> Each individual drive is incredibly consistent in its performance. But
> drive 1 is over 4% faster than drive 2.
>
> The difference can be seen in a graph comparing one full write run of each:
> https://cdna.pcpartpicker.com/static/forever/images/content/221396115ee6bae8fbd35135fbc6441e.png