On Thu, Oct 31, 2024 at 3:06 PM Keith Busch [off-list ref] wrote:

On Thu, Oct 31, 2024 at 09:19:51AM +0100, Hans Holmberg wrote:

quoted

On Wed, Oct 30, 2024 at 11:33 PM Keith Busch [off-list ref] wrote:

quoted

That is very much apples-to-oranges. The B+ isn't on the same device
being evaluated for WAF, where this has all that mixed in. I think the
results are pretty good, all things considered.

No. The meta data IO is just 0.1% of all writes, so that we use a
separate device for that in the benchmark really does not matter.

It's very little spatially, but they overwrite differently than other
data, creating many small holes in large erase blocks.

I don't really get how this could influence anything significantly.(If at all).

quoted

Since we can achieve a WAF of ~1 for RocksDB on flash, why should we
be content with another 67% of unwanted device side writes on top of
that?

It's of course impossible to compare your benchmark figures and mine
directly since we are using different devices, but hey, we definitely
have an opportunity here to make significant gains for FDP if we just
provide the right kernel interfaces.

Why shouldn't we expose the hardware in a way that enables the users
to make the most out of it?

Because the people using this want this interface. Stalling for the last
6 months hasn't produced anything better, appealing to non-existent
vaporware to block something ready-to-go that satisfies a need right
now is just wasting everyone's time.

Again, I absolutely disagree that this locks anyone in to anything.
That's an overly dramatic excuse.

Locking in or not, to constructively move things forward (if we are
now stuck on how to wire up fs support) I believe it would be
worthwhile to prototype active fdp data placement in xfs and evaluate
it. Happy to help out with that.

Fdp and zns are different beasts, so I don't expect the results in the
presentation to be directly translatable but we can see what we can
do.

Is RocksDB the only file system user at the moment?
Is the benchmark setup/config something that could be shared?