Re: [PATCH v4 00/13] support non power of 2 zoned devices

Javier González
2022-05-17T09:19:15Z

On 17.05.2022 10:10, Christoph Hellwig wrote:
>I'm a little surprised about all this activity.
>
>I though the conclusion at LSF/MM was that for Linux itself there
>is very little benefit in supporting this scheme. It will massively
>fragment the supported based of devices and applications, while only
>having the benefit of supporting some Samsung legacy devices.

I believed we had agreed that non-power-of-2 zoned devices was something
to explore. Let me summarize the 3 main points we covered at different
times at LSF/MM:

- This is not for legacy Samsung ZNS devices. At least 4 other
vendors have reported building non-power-of-2 ZNS devices to meet
customer demands on removing holes in the address space. It seems
like there will be more ZNS devices with size=capacity out there
than with PO2 sizes. Block device and FS support is very desirable
for these.

- We also talked about how the capacity not being a PO2 is the one
introducing the fragmentation, as applications that already worked
with SMR HDDs will have to change their data placement policy. The
size is just a construction, but the real work is adopting the
capacity.

- Besides the previous poit, the fragmentation will happen from the
moment we have available devices. This is not a kernel-only issue.
We have SMR, ZNS, and soon another spec for zone devices. I
understood that as long as we do not break any existing support, we
would be able to expend the zoned ecosystem in Linux.

>So my impression was that this work, while technically feasible, is
>rather useless. So unless I missed something important I have no
>interest in supporting this in NVMe.

Does the above help you reconsidering your interest in supporting this
in NVMe?