Re: [PATCHv11 0/9] write hints with nvme fdp and scsi streams

Christoph Hellwig
2024-11-12T17:19:21Z

On Tue, Nov 12, 2024 at 05:50:54PM +0100, Christoph Hellwig wrote:
> > so putting the filesystem in the way to force
> > streams look like zones is just a unnecessary layer of indirection
> > getting in the way.
>
> Can you please stop this BS? Even if a file system doesn't treat
> write streams like zones keeps LBA space and physical allocation units
> entirely separate (for which I see no good reason, but others might
> disagree) you still need the file system in control of the hardware
> resources.

And in case this wasn't clear enough. Let's assume you want to write
a low write amp flash optimized file system similar to say the storage
layers of the all flash arrays of the last 10-15 years.

You really want to avoid device GC. You'd better group your data to
the reclaim unit / erase block / insert name here. So you need file
system control of the write streams, you need to know their size,
you need to be able to query how much your wrote after a power faіl.
Totally independent of how you organize your LBA space. Mapping
it linearly might be the easier options without major downside, but
you could also allocate them randomly for that matter.

>
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