On Thu, Aug 21, 2014 at 03:28:42PM -0700, Howard Chu wrote: > maxsize is the back-mdb keyword. mapsize is the LMDB API property. They > both refer to the same thing. We used the word "maxsize" for back-mdb to > impress upon sysadmins that this really is a long-term maximum, and not a > setting that should be tuned on an ongoing basis.
Ok, that explains the terminology. > >Can 'maxsize' ever be reduced after the fact? If so, is their > >guidance as to how much it can change (perhaps based on mdb_stat)? > > Read the LMDB documentation. What, this: http://symas.com/mdb/doc/ ? A search for 'maxsize' or 'mapsize' yeilds no hits. The mdb_stats manpage tells me how to invoke it, but not how to interpret the results. I have seen other messages to this mailing list provide some guidance, but nothing that seemed to directly apply to my questions. Perhaps I'm missing some keyword somewhere. > >My naive use of the LDMB backend has me assume the worst case, and > >now everyone is equally punished for having a 'big' (albeit sparse) > >database. > > "Punished"? There is no penalty for configuring a large maxsize, no matter > how small the actual data. The 'punishment' is multifold: - consumption of diskspace for storage (our database is stored on the same partition as our backups; perhaps not the best of plans). - the time it takes to compress/uncompress a backup. - the network bandwidth cost of transmitting a file that's larger than it needs to be. > -- > -- Howard Chu > CTO, Symas Corp. http://www.symas.com > Director, Highland Sun http://highlandsun.com/hyc/ > Chief Architect, OpenLDAP http://www.openldap.org/project/ -- Brian Reichert <[email protected]> BSD admin/developer at large
