{"id":2006,"date":"2018-08-21T16:29:00","date_gmt":"2018-08-21T16:29:00","guid":{"rendered":"http:\/\/dbtut.com\/?p=2006"},"modified":"2018-11-11T21:08:54","modified_gmt":"2018-11-11T21:08:54","slug":"fragmentation-on-mongodb-databases","status":"publish","type":"post","link":"https:\/\/dbtut.com\/index.php\/2018\/08\/21\/fragmentation-on-mongodb-databases\/","title":{"rendered":"Fragmentation on MongoDB databases"},"content":{"rendered":"

 <\/p>\n

Fragmentation on MongoDB databases<\/span><\/p>\n

When we removing a large amount of data from the collection and no plan to replace it, we generate a fragmentation, to deal with it, we have a COMPACT command.<\/p>\n

The compact command rewrites and defragments all data and indexes in a collection, depending on what storage engine we have.<\/p>\n

Differences between Storage – Engines (included in community\u00a0edition)<\/span><\/strong><\/p>\n\n\n\n\n\n\n
COMMAND<\/b><\/td>\nMMAPV1<\/b><\/td>\nWIREDTIGER<\/b><\/td>\n<\/tr>\n
COMPACT<\/td>\nOn MMAPv1, compact defragments the collection\u2019s data files and recreates its indexes. Unused disk space is not released to the system<\/i><\/b> but instead retained for future data.<\/td>\nOn WiredTiger, compact attempts to reduce the required storage space for data and indexes in a collection, releasing unneeded disk space to the operating system.<\/strong><\/td>\n<\/tr>\n
COMPACT<\/td>\nCompact\u00a0requires up to 2 gigabytes of additional disk space to run on MMAPv1 databases.<\/td>\nCompact does not require any additional disk space to run on WiredTiger databases<\/td>\n<\/tr>\n
COMPACT<\/td>\n\u00a0If you wish to reclaim disk space from an MMAPv1 database, you should perform an initial sync.<\/td>\n–<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Considerations:<\/span><\/strong><\/p>\n

    \n
  • Always have an up-to-date backup before performing server maintenance such as the compact operation.<\/li>\n
  • Compact only blocks operations for the database it is currently operating on. Only use compact during scheduled maintenance periods<\/i><\/b>.<\/i><\/b><\/li>\n
  • Compact command do not replicate to secondaries in a ReplicaSet\n
      \n
    • Compact each member separately<\/li>\n
    • Ideally run compact on a secondary, this command forces to enter en recovering state<\/li>\n<\/ul>\n<\/li>\n
    • Shared Clusters\n
        \n
      • Compact only applies to a mongod instance, In a shared environment, run compact on each shard separately as a maintenance\u00a0operation.<\/li>\n<\/ul>\n<\/li>\n
      • Index Building\n
          \n
        • mongod rebuilds all indexes in parallel following the compact operation<\/li>\n<\/ul>\n<\/li>\n
        • I recommend applying\u00a0the compact operation if the result of the next formula is greater than 15%\n
            \n
          • 100% – (Data + Indexes) \/ storage > 15%<\/li>\n<\/ul>\n<\/li>\n
          • On databases larger than a few gigs can take\u00a0a while to complete<\/li>\n<\/ul>\n

            Compacting and Compressing are two different things, please don\u00b4t confuse. These two concepts are totally different in MongoDB.<\/p>\n\n

            <\/div>\n

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            <\/div>\n","protected":false},"excerpt":{"rendered":"

              Fragmentation on MongoDB databases When we removing a large amount of data from the collection and no plan to replace it, we generate a fragmentation, to deal with it, we have a COMPACT command. The compact command rewrites and defragments all data and indexes in a collection, depending on what storage engine we have. …<\/p>\n

            <\/div>\n

            <\/path><\/svg><\/i> \"Loading\"<\/p>\n

            <\/div>\n","protected":false},"author":67,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"_uf_show_specific_survey":0,"_uf_disable_surveys":false,"footnotes":""},"categories":[1306,1388],"tags":[1410,1409,1406,171,1405,1371,1407,1408],"class_list":["post-2006","post","type-post","status-publish","format-standard","","category-mongodb","category-nosql","tag-collection","tag-database","tag-fragmentation","tag-index","tag-mmapv1","tag-mongodb","tag-storage-engine","tag-wiredtiger"],"aioseo_notices":[],"yoast_head":"\nFragmentation on MongoDB databases - Database Tutorials<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/dbtut.com\/index.php\/2018\/08\/21\/fragmentation-on-mongodb-databases\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Fragmentation on MongoDB databases - Database Tutorials\" \/>\n<meta property=\"og:description\" content=\"  Fragmentation on MongoDB databases When we removing a large amount of data from the collection and no plan to replace it, we generate a fragmentation, to deal with it, we have a COMPACT command. 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