Checking disk I/O usage

As explained in Chapter 2, Understanding and Managing Indexes, MongoDB's performance is greatly dependent on the system's available memory and disk type. In this recipe, we will look at a few tools and MongoDB commands that can help us identify disk I/O utilization.

Getting ready

You need a single-node MongoDB instance.

How to do it...

1. In a mongo shell, execute the db.serverStatus() command:

db.serverStatus()

2. You should see output similar to this:

{ 
    "host" : "vagrant-ubuntu-trusty-64",
    "version" : "3.4.6",
    "process" : "mongod",
    "pid" : NumberLong(20657),
    "uptime" : 5626,
    "uptimeMillis" : NumberLong(5625427),
    "uptimeEstimate" : NumberLong(5625),
    "localTime" : ISODate("2017-10-10T10:02:49.306Z"),
    "asserts" : {
        "regular" : 0,
        "warning" : 0,
        "msg" : 0,
        "user" : 0,
        "rollovers" : 0
    },
    "backgroundFlushing" : {
        "flushes" : 93,
        "total_ms" : 457,
        "average_ms" : 4.913978494623656...