On 6/9/21 5:32 PM, Jaegeuk Kim wrote:
On Wed, Jun 9, 2021 at 11:47 AM Bart Van Assche <bvanassche@xxxxxxx
<mailto:bvanassche@xxxxxxx>> 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"
Do you agree with that statement based on your insight? At least to me, that
paper is missing the fundamental GC problem which was supposed to be
evaluated by real workloads instead of using a simple benchmark generating
4KB random writes only. And, they had to investigate more details in FTL/IO
patterns including UNMAP and LBA alignment between host and storage, which
all affect WAF. Based on that, the point of the zoned device is quite promising
to me, since it can address LBA alignment entirely and give a way that host
SW stack can control QoS.
Just a note, using a pretty simple and optimal streaming write pattern, I have
been able to burn out emmc parts in a little over a week.
My test case creating a 1GB file (filled with random data just in case the
device was looking for zero blocks to ignore) and then do a loop to cp and sync
that file until the emmc device life time was shown as exhausted.
This was a clean, best case sequential write so this is not just an issue with
small, random writes.
Of course, this is normal to wear them out, but for the super low end parts,
taking away any of the device writes in our stack is costly given how little
life they have....
Regards,
Ric
The topic has been a long-standing issue in flash area for multiple years and
it'd be exciting to see any new ideas.
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.
