Hi Will, Yes, adding new pools will increase the number of PG's per OSD. But you can always decrease the number of pg's per OSD by adding new Hosts/OSD's.
When you design a cluster you have to calculate how many pools you're going to use and use that information with PGcalc. (https://ceph.com/pgcalc/) If you add pools later on they were not part of the original design and you probably will need additional space (OSD's) too. Kind regards, Caspar 2018-03-09 11:05 GMT+01:00 Will Zhao <zhao6...@gmail.com>: > Hi Janne: > Thanks for your response. Approximately 100 PGs per OSD, yes, I > missed out this part. > I am still a little confused. Because 100-PGs-per-OSD rule is the > result of sumation of all used pools . > I konw I can create many pools.Assume that I have 5 pools now , and > the rule has already been met. > So if I create the sixth pool, the total PGs will increased , then > the PGs per OSD will be more then 100. > Will this not violate the rule ? > > > On Fri, Mar 9, 2018 at 5:40 PM, Janne Johansson <icepic...@gmail.com> > wrote: > > > > > > 2018-03-09 10:27 GMT+01:00 Will Zhao <zhao6...@gmail.com>: > >> > >> Hi all: > >> > >> I have a tiny question. I have read the documents, and it > >> recommend approximately 100 placement groups for normal usage. > > > > > > Per OSD. Approximately 100 PGs per OSD, when all used pools are summed > up. > > For things like radosgw, let it use the low defaults (8?) and then > expand on > > the pools > > that actually see a lot of data getting into them, leave the rest as is. > > > > > >> > >> Because the pg num can not be decreased, so if in current cluster, > >> the pg num have met this rule, and when I try to create a new pool , > >> what pg num I should set ? I think no matter what I do , it will > >> violate the pg-num-rule, add burden to osd. This means , if I want my > >> cluster be used by many different users, I should bulid a new cluster > >> for new user ? > >> > > > > No, one cluster can serve a lot of clients. You can have lots of pools if > > you need, > > and those pools can have separate OSD hosts serving them if you need > strong > > separation, but still managed from the same cluster. > > > > -- > > May the most significant bit of your life be positive. > _______________________________________________ > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >
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