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  1. Documentation
  2. DOCS-126

Add more details to the Lots of Collections wiki page

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    • Icon: Bug Bug
    • Resolution: Done
    • Icon: Major - P3 Major - P3
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    Description

      Considering the scale of data most people considering the "Lots of Collections" route have, I feel the page could use a lot more detailed information about the ramifications of choosing to use lots of collections.

      The following is what I added to my internal wiki:

      === Namespaces ===

      • namespaces = collections + indexes and are per-database (stored in a db.ns file)
      • Check namespaces with ''db.system.namespaces.count()'' (safe & cheap)
      • ''show collections'' in the mongo shell will no longer work
      • ~600 bytes per namespace on disk
      • namespaces are stored in a hashtable
      • so you should only fill the namespace table up to ~75%
      • namespace database is statically sized on server startup
      • change with --nssize
      • defaults to 16mb
      • can go up to 2047mb (docs say 2GB, but --nssize=2048 crashes)
      • db.ns file is created and zeroed to nssize //the first time data is inserted into the database//
      • So we'd need to be careful creating test dbs on busy servers with high nssizes

      == Limits ==

      Limits are approximate due to the fact hash tables should never be full.

      • Default: *20k*
      • Maximum: *2.5m*

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            kay.kim@mongodb.com Kay Kim (Inactive)
            schmichael Michael Schurter
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            Dates

              Created:
              Updated:
              Resolved:
              11 years, 51 weeks ago