On Tuesday, January 22, 2013 at 1:57 PM, Mark Nelson wrote: > On 01/22/2013 03:50 PM, Stefan Priebe wrote: > > Hi, > > Am 22.01.2013 22:26, schrieb Jeff Mitchell: > > > Mark Nelson wrote: > > > > It may (or may not) help to use a power-of-2 number of PGs. It's > > > > generally a good idea to do this anyway, so if you haven't set up your > > > > production cluster yet, you may want to play around with this. Basically > > > > just take whatever number you were planning on using and round it up (or > > > > down slightly). IE if you were going to use 7,000 PGs, round up to 8192. > > > > > > > > > > > > As I was asking about earlier on IRC, I'm in a situation where the docs > > > did not mention this in the section about calculating PGs so I have a > > > non-power-of-2 -- and since there are some production things running on > > > that pool I can't currently change it. > > > > > > > > Oh same thing here - did i miss the doc or can someone point me the > > location. > > > > Is there a chance to change the number of PGs for a pool? > > > > Greets, > > Stefan > > > > Honestly I don't know if it will actually have a significant effect. > ceph_stable_mod will map things optimally when pg_num is a power of 2, > but that's only part of how things work. It may not matter very much > with high PG counts. IIRC, having a non-power of 2 count means that the extra PGs (above the lower-bounding power of 2) will be twice the size of the other PGs. For reasonable PG counts this should not cause any problems. -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
