© 2012 10gen, the MongoDB Company

Authors: Andrea Lattuada

The commands used by this tool are currently EXPERIMENTAL and UNSUPPORTED.

Storage-viz is a suite of web-based visualizers that leverage new database commands: they make it easier to understand and analyze MongoDB storage and btree layout.

The storageDetails command will aggregate statistics related to the storage layout (when invoked with analyze: "diskStorage") or the percentage of pages currently in RAM (when invoked with analyze: "pagesInRAM") for the specified collection, extent or part of extent.

The indexStats command provides detailed and aggregate information and statistics for the underlying btree of a particular index. Stats are aggregated for the entire tree, per-depth and, if requested through the expandNodes option, per-subtree.

Both commands take a global READ_LOCK and will page in all the extents or btree buckets encountered: this will have adverse effects on server performance. The commands should never be run on a primary and will cause a secondary to fall behind on replication. diskStorage when run with analyze: "pagesInRAM" is the exception as it typically returns rapidly and may only page in extent headers.

To use the commands and visualizers you need a recent MongoDB Nightly build.

You can enable the experimental commands with

    --enableExperimentalStorageDetailsCmd

or

    --enableExperimentalIndexStatsCmd

NOTE: running mongod with these options is unsafe and not advisable for production servers.

If you'd like to run the commands directly within the shell, helpers are available.

Json output:

db.collection.diskStorageStats({...})
db.collection.pagesInRAM({...})
db.collection.indexStats({index: "index name", ...})

Their counterparts providing human-readable output follow.

db.collection.getDiskStorageStats({...})
db.collection.getPagesInRAM({...})
db.collection.getIndexStats({...})

To use the visualizers the server needs to be started with the --rest --jsonp command line flags.

NOTE: running mongod with these options is unsafe and not advisable for production servers. Moreover, --rest --jsonp allows anyone on the same network as the server to invoke commands and query or modify data.

The visualizers provide a nicer graphical representation but are very early stage and have only been tested in Chrome. The source code for them is available in this repository.

https://utaal.github.com/mongovis/diskStorageStats.html displays storage layout and usage.

https://utaal.github.com/mongovis/indexStats.html shows statistics related to the indexing btrees.

https://utaal.github.com/mongovis/pagesInRAM.html reports which parts of a collection is currently in ram.

If you'd like to report a bug or request a new feature, please file an issue on our github repository (you must be logged into github to do this):

https://github.com/10gen-labs/storage-viz/issues/new