On Fri, Mar 24, 2017 at 8:08 PM, Spandan Kumar Sahu <spandankumarsahu@xxxxxxxxx> wrote: > I understand that, we can't write to objects which belong to the > particular PG (the one having at least one full OSD). But a storage > pool can have multiple PGs, and some of them must have only non-full > OSDs. Through those PGs, we can write to the OSDs which are not full. but we cannot impose the restriction on the client that only a subset of PGs of the given pool can be written. > > Did I understand it correctly? > > > On Fri, Mar 24, 2017 at 1:01 PM, kefu chai <tchaikov@xxxxxxxxx> wrote: >> Hi Spandan, >> >> Please do not email me privately, instead use the public mailing list, >> which allows other developers to provide you help if I am unable to do >> so. it also means that you can start interacting with the rest of the >> community instead of only me (barely useful). >> >> On Fri, Mar 24, 2017 at 2:38 PM, Spandan Kumar Sahu >> <spandankumarsahu@xxxxxxxxx> wrote: >>> Hi >>> >>> I couldn't figure out, why is this happening, >>> >>> "...Because once any of the storage device assigned to a storage pool is >>> full, the whole pool is not writeable anymore, even there is abundant space >>> in other devices." >>> -- Ceph GSoC Project Ideas (Smarter reweight-by-utilisation) >>> >>> I went through this[1] paper on CRUSH, and according to what I understand, >>> CRUSH pseudo-randomly chooses a device based on weights which can reflect >>> various parameters like the amount of space available. >> >> CRUSH is a variant of consistent hashing. Ceph cannot automatically >> choose *another* OSD which is not chosen by CRUSH, even if that OSD is >> not full and has abundant space. >> >>> >>> What I don't understand is, how will it stop a pool having abundant space on >>> other devices, from getting selected, if one of its devices is full? Sure, >>> the chances of getting selected might decrease, if one device is full, but >>> how does it completely prevent writing to the pool? >> >> if a PG are served by three OSDs. if any of them is full, how can we >> continue creating/writing to objects which belong to that PG? >> >> >> -- >> Regards >> Kefu Chai > > > > -- > Spandan Kumar Sahu > IIT Kharagpur -- Regards Kefu Chai -- 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
