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

[Keith Busch <kbusch@kernel.org>]

On Thu, Jun 10, 2021 at 11:07:09AM +0000, Tim Walker wrote:
>  Wednesday, June 9, 2021 at 9:20:52 PM Ric Wheeler wrote:
> >On 6/9/21 2:47 PM, Bart Van Assche wrote:
> >> On 6/9/21 11:30 AM, Matthew Wilcox wrote:
> >>> 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"
> >> It seems like my email was not clear enough? What I tried to make clear
> >> is that I think that there is no way to solve the flash wear issue with
> >> the traditional block interface. I think that F2FS in combination with
> >> the zone interface is an effective solution.
> >>
> >> What is also relevant in this context is that the "Flash drive lifespan
> >> is a problem" paper was published in 2017. I think that the first
> >> commercial SSDs with a zone interface became available at a later time
> >> (summer of 2020?).
> >>
> >> Bart.
> >
> >Just to address the zone interface support, it unfortunately takes a very long 
> >time to make it down into the world of embedded parts (emmc is super common and 
> >very primitive for example). UFS parts are in higher end devices, have not had a 
> >chance to look at what they offer.
> >
> >Ric
> 
> For zoned block devices, particularly the sequential write zones,
> maybe it makes more sense for the device to manage wear leveling on a
> zone-by-zone basis. It seems like it could be pretty easy for a device
> to decide which head/die to select for a given zone when the zone is
> initially opened after the last reset write pointer.

I think device managed wear leveling was the point of zoned ssd's. If the
host was managing that, then that's pretty much an open channel ssd.