Part of the answer is that going "readable" with read_min_size
replicas has a side effect of committing any writes those replicas
happen to know about whether they were actually committed to
write_min_size replicas or not because once we've served a read
reflecting those writes, all future reads must also reflect those
writes.

-Sam

On Thu, Dec 24, 2020 at 6:14 AM Prasad Krishnan
<prasad.krishnan@flipkart.com> wrote:
>
> Dear Ceph developers,
>
> Presently Ceph has a single config option named min_size which decides the minimum number of copies that must be available before any client I/O operation (read or write) can be performed on a given RADOS pool.
>
> Would it make sense to split it into two i.e. read_min_size and write_min_size to allow better data availability?
>
> For instance, in a pool with replication size of 3 (where 3 copies are stored), if two OSDs go down, we would want to avoid client write operations (to reduce risk of data loss) but allow client read operations from the single copy that is available. This can be done by setting read_min_size to 1, but retaining write_min_size to 2.
>
> Are there any technical reasons why this cannot work? Any pitfalls that I don't foresee?
>
> Thanks,
> K.Prasad
>
>
>
>
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