Hello, thank you for your response.
Erasure Coding gets better and we really cannot afford the storage
overhead of x3 replication.
Anyway, as I understand the problem, it is also present with
replication, just less amplified (blocks are not divided between OSDs,
just replicated fully).
Le 2021-02-02 16:50, Steven Pine a écrit :
> You are unlikely to avoid the space amplification bug by using larger
> block sizes. I honestly do not recommend using an EC pool, it is
> generally less performant and EC pools are not as well supported by
> the ceph development community.
>
> On Tue, Feb 2, 2021 at 5:11 AM Gilles Mocellin
> <gilles.mocellin(a)nuagelibre.org> wrote:
>
>> Hello,
>>
>> As we know, with 64k for bluestore_min_alloc_size_hdd (I'm only
>> using
>> HDDs),
>> in certain conditions, especially with erasure coding,
>> there's a leak of space while writing objects smaller than 64k x k
>> (EC:k+m).
>>
>> Every object is divided in k elements, written on different OSD.
>>
>> My main use case is big (40TB) RBD images mounted as XFS filesystems
>> on
>> Linux servers,
>> exposed to our backup software.
>> So, it's mainly big files.
>>
>> My though, but I'd like some other point of view, is that I could
>> deal
>> with the amplification by using bigger block sizes on my XFS
>> filesystems.
>> Instead of reducing bluestore_min_alloc_size_hdd on all OSDs.
>>
>> What do you think ?
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>
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> Steven Pine
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