Re: [LSF/MM/BPF TOPIC] durability vs performance for flash devices (especially embedded!)

On Wed, Jun 09, 2021 at 11:05:22AM -0700, Bart Van Assche wrote:

On 6/9/21 3:53 AM, Ric Wheeler wrote:

quoted

Consumer devices are pushed to use the highest capacity emmc class
devices, but they have horrible write durability.

At the same time, we layer on top of these devices our normal stack -
device mapper and ext4 or f2fs are common configurations today - which
causes write amplification and can burn out storage even faster. I think
it would be useful to discuss how we can minimize the write
amplification when we need to run on these low end parts & see where the
stack needs updating.

Great background paper which inspired me to spend time tormenting emmc
parts is:

http://www.cs.unc.edu/~porter/pubs/hotos17-final29.pdf

Without having read that paper, has zoned storage been considered? F2FS
already supports zoned block devices. I'm not aware of a better solution
to reduce write amplification for flash devices. Maybe I'm missing
something?

maybe you should read the paper.

" Thiscomparison demonstrates that using F2FS, a flash-friendly file
sys-tem, does not mitigate the wear-out problem, except inasmuch asit
inadvertently rate limitsallI/O to the device"

More information is available in this paper:
https://dl.acm.org/doi/pdf/10.1145/3458336.3465300.

Thanks,

Bart.