> On Nov 18, 2016, at 6:11 AM, John Spray <jspray@xxxxxxxxxx> wrote: > > On Fri, Nov 18, 2016 at 1:48 PM, Sebastien Han <shan@xxxxxxxxxx> wrote: >> Thanks John that makes sense, since we miss user's overall intent >> there is no point of doing this within the mons :). >> It would be nice to have something a bit more dynamic though, where we >> can decrease PGs based on the topology and the current number of >> pools... Of course this will trigger movements but this is not an >> issue for Ceph :). > > Yeah, being able to decrease pg_num (i.e. do pg joins on the OSDs) > would solve a lot of usability problems: currently we have no choice > but to educate users about PGs on day 1 in order for them to decide > how many they want in a pool. If we could auto-guess, and then > decrease later if we get it wrong, then most users would not need to > know what a PG is to do normal operations. > > I would envision any auto-decrease in pg_num working in concert with a > guided pool creation process; as well as recommending how many pgs new > pools should have, we would recommend any decrease in existing pools, > and provide information about the expected cost of the associated data > movement. > > John > This auto adjusting pg_num logic is a great idea. I would love to see this happen. Nitin >> >> On Thu, Nov 17, 2016 at 10:02 PM, John Spray <jspray@xxxxxxxxxx> wrote: >>> On Thu, Nov 17, 2016 at 6:14 PM, Sebastien Han <shan@xxxxxxxxxx> wrote: >>>> Hey, >>>> >>>> I was wondering, since we have PG calc online to decide the right >>>> value for our PGs per pool. The logic seems to be easy and well >>>> understood. Looks like a simple calculation, I don't see anything like >>>> depending on a use case we are changing the value or anything. >>>> >>>> Any reason why this logic is not part of Ceph? >>>> Mons know about everything on the cluster and since they manage pool >>>> creations they should be able to take the right decision. >>>> >>>> Am I missing something? >>> >>> I think the reason nobody has done this so far is that there's no >>> overall (multiple pools at a time) setup interface in Ceph. To do the >>> pg calc stuff, you need a user to tell you not just that they want a >>> pool, but how many pools they want and what they will use them for: >>> something friendlier than the current "osd pool create" command can >>> handle. >>> >>> Having mons do any kind of guessing on a "pool at a time" basis >>> without visibility of the user's overall intent is pretty dangerous, >>> because users can never fix a bad automatic choice (can't decrease >>> pg_num). >>> >>> John >>> >>>> Thanks! >>>> >>>> -- >>>> Cheers >>>> >>>> –––––– >>>> Sébastien Han >>>> Principal Storage Architect >>>> >>>> "Always give 100%. Unless you're giving blood." >>>> >>>> Mail: seb@xxxxxxxxxx >>>> Address: 11 bis, rue Roquépine - 75008 Paris >>>> -- >>>> 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 >> >> >> >> -- >> Cheers >> >> –––––– >> Sébastien Han >> Principal Storage Architect >> >> "Always give 100%. Unless you're giving blood." >> >> Mail: seb@xxxxxxxxxx >> Address: 11 bis, rue Roquépine - 75008 Paris > -- > 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 ��.n��������+%������w��{.n����z��u���ܨ}���Ơz�j:+v�����w����ޙ��&�)ߡ�a����z�ޗ���ݢj��w�f
