linux-kernel - Re: [f2fs-dev] [PATCH 3/3 v2] f2fs: kill zone-capacity support

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Date: Thu, 22 Feb 2024 15:33:40 +0100
From: Matias Bjørling <m@...rling.me>
To: Jaegeuk Kim <jaegeuk@...nel.org>, Juhyung Park <qkrwngud825@...il.com>
Cc: Niklas Cassel <niklas.cassel@....com>,
 Damien Le Moal <damien.lemoal@....com>, daehojeong@...gle.com,
 linux-kernel@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net,
 Matias Bjørling <matias.bjorling@....com>
Subject: Re: [f2fs-dev] [PATCH 3/3 v2] f2fs: kill zone-capacity support

On 21-02-2024 18:27, Jaegeuk Kim wrote:

>> Doesn't this break practically all ZNS NVMe devices?
> 
> Yes, so here I'm in questioning who is really using w/ zone capacity. If there's
> no user complaining, I'd like to deprecate this, since this adds code complexity
> and unnecessary checks.
> 

Hi Jaegeuk,

I like to make a couple of points to hopefully keep the support in a 
little while longer.

- NVMe-based zone devices continue to be developed with the pow2 zone 
size and zone size != zone cap features. There was some divergence in 
the first-gen drives. However, all the second-gen drives I know of are 
implemented with those features in mind.

- A very active community is doing work using f2fs, and many of those 
members are working with the ZN540s device (which exposes a pow2 zone size).

- For drives with a capacity of less than 16TiB, f2fs is an excellent 
file system to use and is really useful for various use cases. We're 
using the f2fs daily for a couple of our workloads.

Work is ongoing on btrfs and XFS to support zoned storage devices, but 
they have yet to be through the trenches as much as f2fs has been with 
its zone support. So it would be great to have f2fs continue to support 
the pow2 zone sizes, as it is a valuable feature for the currently used 
and second-gen drives that have been released or are soon becoming 
available.

If there is a performance concern with the feature re: ZUFS, maybe the 
pow2 implementation could be slightly more computationally expensive, as 
the feature, anyway, typically is used on more beefy systems.

Regards,
Matias