On Tue, Oct 27, 2015 at 11:47 AM, GuangYang <yguang11@xxxxxxxxxxx> wrote: > Hi there, > Is there any reason we stuck read only requests as well for a PG when the acting set size is less than min_size? A few. The most important reason: PGs don't have any concept of a read-only mode in the code. They are "active" or not, and an active PG handles writes. (The full flags and other things which block writes but allow reads are at the OSD level, not the PG level, and are handled when ops come in before they reach the PG.) Allowing read requests against a PG to complete even when we aren't taking writes on a per-PG level would take some doing. Also: it would be weird from several different levels. We'd need to keep track of client streams because we wouldn't want to let through a read that is ordered after a write. How would we handle the memory pressure implied by that? While I can imagine it being useful for some stuff like RGW reads, in general making data available for read but not write is a pretty complicated thing to explain to users — how do we expose that in a useful way? -Greg -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
