compression, ocean data 2.6 vs 3.0

gistfile1.js

Consider:

> db.ocean_data.findOne()
{
	"_id" : ObjectId("53e4fcc42239c23dce3cb7bc"),
	"station_id" : 8461490,
	"loc" : {
		"type" : "Point",
		"coordinates" : [
			-72.09,
			41.3614
		]
	},
	"name" : "New London",
	"products" : [
		{
			"v" : 69.4,
			"t" : ISODate("2014-08-08T16:24:00Z"),
			"name" : "water_temperature",
			"f" : "0,0,0"
		},
		{
			"v" : 77,
			"t" : ISODate("2014-08-08T16:24:00Z"),
			"name" : "air_temperature",
			"f" : "0,0,0"
		},
		{
			"d" : "360.00",
			"g" : "8.75",
			"f" : "0,0",
			"s" : "4.08",
			"t" : ISODate("2014-08-08T16:24:00Z"),
			"dr" : "N",
			"name" : "wind"
		},
		{
			"v" : 1015.8,
			"t" : ISODate("2014-08-08T16:24:00Z"),
			"name" : "air_pressure",
			"f" : "0,0,0"
		}
	],
	"fetch_date" : ISODate("2014-08-08T16:37:22.640Z"),
	"id" : 8461490
}

> db.ocean_data.stats()
{
	"ns" : "admin.ocean_data",
	"count" : 4227631,
	"size" : 2269568784,
	"avgObjSize" : 536,
	"storageSize" : 2653351904,
	"numExtents" : 21,
	"nindexes" : 5,
	"lastExtentSize" : 536600560,
	"paddingFactor" : 1,
	"systemFlags" : 1,
	"userFlags" : 1,
	"totalIndexSize" : 1712397792,
	"indexSizes" : {
		"_id_" : 244388816,
		"station_id_hashed" : 265417488,
		"loc_2dsphere" : 283004064,
		"products.t_-1" : 167885984,
		"products.name_-1" : 751701440
	},
	"ok" : 1
}

> db.ocean_data.stats()
{
	"ns" : "admin.ocean_data",
	"count" : 4227631,
	"size" : 1772605820,
	"avgObjSize" : 419,
	"storageSize" : 684040192,
	"capped" : false,
	"wiredTiger" : {
		"metadata" : {
			"formatVersion" : 1
		},
		"creationString" : "allocation_size=4KB,app_metadata=(formatVersion=1),block_allocation=best,block_compressor=snappy,cache_resident=0,checkpoint=(WiredTigerCheckpoint.2=(addr=\"01e3026c1681e47b5d2885e3026c1781e44d1019d8e3026c1881e4be07f0e6808080e428c57fc0e428c48fc0\",order=2,time=1427150035,size=683978752,write_gen=55965)),checkpoint_lsn=(22,68783744),checksum=uncompressed,collator=,columns=,dictionary=0,format=btree,huffman_key=,huffman_value=,id=14,internal_item_max=0,internal_key_max=0,internal_key_truncate=,internal_page_max=4KB,key_format=q,key_gap=10,leaf_item_max=0,leaf_key_max=0,leaf_page_max=32KB,leaf_value_max=1MB,memory_page_max=10m,os_cache_dirty_max=0,os_cache_max=0,prefix_compression=0,prefix_compression_min=4,split_deepen_min_child=0,split_deepen_per_child=0,split_pct=90,value_format=u,version=(major=1,minor=1)",
		"type" : "file",
		"uri" : "statistics:table:collection-11-7990094587935123507",
		"LSM" : {
			"bloom filters in the LSM tree" : 0,
			"bloom filter false positives" : 0,
			"bloom filter hits" : 0,
			"bloom filter misses" : 0,
			"bloom filter pages evicted from cache" : 0,
			"bloom filter pages read into cache" : 0,
			"total size of bloom filters" : 0,
			"sleep for LSM checkpoint throttle" : 0,
			"chunks in the LSM tree" : 0,
			"highest merge generation in the LSM tree" : 0,
			"queries that could have benefited from a Bloom filter that did not exist" : 0,
			"sleep for LSM merge throttle" : 0
		},
		"block-manager" : {
			"file allocation unit size" : 4096,
			"blocks allocated" : 0,
			"checkpoint size" : 683978752,
			"allocations requiring file extension" : 0,
			"blocks freed" : 0,
			"file magic number" : 120897,
			"file major version number" : 1,
			"minor version number" : 0,
			"file bytes available for reuse" : 53248,
			"file size in bytes" : 684040192
		},
		"btree" : {
			"column-store variable-size deleted values" : 0,
			"column-store fixed-size leaf pages" : 0,
			"column-store internal pages" : 0,
			"column-store variable-size leaf pages" : 0,
			"pages rewritten by compaction" : 0,
			"number of key/value pairs" : 0,
			"fixed-record size" : 0,
			"maximum tree depth" : 3,
			"maximum internal page key size" : 368,
			"maximum internal page size" : 4096,
			"maximum leaf page key size" : 3276,
			"maximum leaf page size" : 32768,
			"maximum leaf page value size" : 1048576,
			"overflow pages" : 0,
			"row-store internal pages" : 0,
			"row-store leaf pages" : 0
		},
		"cache" : {
			"bytes read into cache" : 71,
			"bytes written from cache" : 0,
			"checkpoint blocked page eviction" : 0,
			"unmodified pages evicted" : 0,
			"page split during eviction deepened the tree" : 0,
			"modified pages evicted" : 0,
			"data source pages selected for eviction unable to be evicted" : 0,
			"hazard pointer blocked page eviction" : 0,
			"internal pages evicted" : 0,
			"pages split during eviction" : 0,
			"in-memory page splits" : 0,
			"overflow values cached in memory" : 0,
			"pages read into cache" : 1,
			"overflow pages read into cache" : 0,
			"pages written from cache" : 0
		},
		"compression" : {
			"raw compression call failed, no additional data available" : 0,
			"raw compression call failed, additional data available" : 0,
			"raw compression call succeeded" : 0,
			"compressed pages read" : 0,
			"compressed pages written" : 0,
			"page written failed to compress" : 0,
			"page written was too small to compress" : 0
		},
		"cursor" : {
			"create calls" : 0,
			"insert calls" : 0,
			"bulk-loaded cursor-insert calls" : 0,
			"cursor-insert key and value bytes inserted" : 0,
			"next calls" : 0,
			"prev calls" : 0,
			"remove calls" : 0,
			"cursor-remove key bytes removed" : 0,
			"reset calls" : 0,
			"search calls" : 0,
			"search near calls" : 0,
			"update calls" : 0,
			"cursor-update value bytes updated" : 0
		},
		"reconciliation" : {
			"dictionary matches" : 0,
			"internal page multi-block writes" : 0,
			"leaf page multi-block writes" : 0,
			"maximum blocks required for a page" : 0,
			"internal-page overflow keys" : 0,
			"leaf-page overflow keys" : 0,
			"overflow values written" : 0,
			"pages deleted" : 0,
			"page checksum matches" : 0,
			"page reconciliation calls" : 0,
			"page reconciliation calls for eviction" : 0,
			"leaf page key bytes discarded using prefix compression" : 0,
			"internal page key bytes discarded using suffix compression" : 0
		},
		"session" : {
			"object compaction" : 0,
			"open cursor count" : 0
		},
		"transaction" : {
			"update conflicts" : 0
		}
	},
	"nindexes" : 5,
	"totalIndexSize" : 179036160,
	"indexSizes" : {
		"_id_" : 55345152,
		"station_id_hashed" : 37826560,
		"loc_2dsphere" : 28094464,
		"products.t_-1" : 14024704,
		"products.name_-1" : 43745280
	},
	"ok" : 1
}