Re: Question: how understand the raid profile of a btrfs filesystem

Andrei Borzenkov
2020-03-21T05:42:40Z

21.03.2020 06:29, Zygo Blaxell пишет:
> On Fri, Mar 20, 2020 at 06:56:38PM +0100, Goffredo Baroncelli wrote:
>> Hi all,
>>
>> for a btrfs filesystem, how an user can understand which is the {data,mmetadata,system} [raid] profile in use ? E.g. the next chunk which profile will have ?
>
> It's the profile used by the highest-numbered block group for the
> allocation type (one for data, one for metadata/system).

Is "highest-numbered" block group always the last one created? Can block
group numbers wrap around?

Recently someone reported that after conversion block groups with old
profile remained and this probably explains it - conversion races with
new allocation.

>> So the question is: the next chunk which profile will have ?
>> Is there any way to understand what will happens ?

Well, from that explanation it is not possible using standard tools -
one needs to crawl btrfs internals to find out the "last" block group.