Re: [RFC ONLY 3/8] btrfs: read raid-stripe-tree from disk

Qu Wenruo
2022-05-19T08:37:01Z

On 2022/5/18 19:29, Johannes Thumshirn wrote:
> On 17/05/2022 10:28, Qu Wenruo wrote:
>>>
>>> Metadata on the stripe tree really is the main blocker right now.
>>
>> That's no doubt.
>
> What could be done and I think this is the only way forward, is to have
> the stripe tree in the system block group

This behavior itself has its problems, unfortunately.

Currently the system chunks are pretty small, in fact system chunks has
the minimal stripe size for current code base.
(Data: 1G, Meta: 1G/256M, sys: 32M)

This means, if we put stripe tree (which can be as large as extent tree
afaik), we need way much larger system chunks.

And this can further increase the possibility on ENOSPC due to
unbalanced data/metadata/sys usage.

Although this is really the last problem we need to bother.

> and force system to be RAID1 on a fs with stripe tree.

Then the system RAID1 chunks also need stripe tree for zoned devices.

This means we're unable to bootstrap at all.

Or did you mean, make system chunks RAID1 but not using stripe tree?
That can solve the boot strap problem, but it doesn't really look
elegant to me...

Thanks,
Qu

>
> Thoughts?