Effect of partitioning on wear-leveling

[Warner Losh]

On Tue, Mar 22, 2016 at 6:11 AM, Jia-Shiun Li <jiashiun at gmail.com> wrote:

> On Tue, Mar 22, 2016 at 2:26 PM, Peter Jeremy <peter at rulingia.com> wrote:
>
> > On 2016-Mar-21 21:47:39 -0600, Warner Losh <imp at bsdimp.com> wrote:
> > >So let’s do the math. 512MB cards tended to have write speeds of maybe
> > 6MB/s.
> > >At 6MB/s, that’s about 518MB/day, or one drive write per day. Most SD
> > cards,
> >
> > I think you dropped some zeroes there.  6MB/s == 518,400MB/day ==
> > 518GB/day.
> > That's 1000 drive writes/day - which is non-trivial.
>

Yes, I must have. I think I must be misremembering the speed. Also, DD speed
on the 512MB drives I just tried is closer to 3MB/s and writes through the
file
system are closer to 1MB for big writes and 500k for small writes... Still
that's
not enough of difference to make up for the while error. Maybe a factor of
10?


> >
> btw at the days of 512MB cards they are mostly made of SLC nand flash,
> some were beginning to transition to MLC. They are different from TLC these
> days in terms of endurance.


That may explain it. SLC parts generally were good for 50k or 100k cycles,
while
MLC parts are good for 2k-5k. TTLC parts maybe 1k. The 1 drive write per day
drives generally are at the low end of MLC or the high end of TLC. So
that's another
factor of 100 there maybe?

Warner