check storage engine from shell

Question

I'm upgrading to 3.0 and ran into some issues with the upgrade. Specifically, I got an error when trying to start up mongod via ssh, it tried to use the default dbpath instead of the one I specified in my new YAML config file. I went ahead and rebooted the machine and now mongod is up and running again. I'm a bit paranoid at this point and would like to know if there's a way to make sure the storage engine is wiredtiger from the shell.

Answer 1

Easiest way to find the storage engine being used currently.

Inside mongo console type

db.serverStatus().storageEngine

It returns the storage engine being used currently

{ "name" : "wiredTiger" }

Once it is confirmed that wiredTiger is being used then type

db.serverStatus().wiredTiger

to get all the configuration details of wiredTiger.

Answer 2

DISCLAIMER : Not a MongoDB Expert

Check the process list in Linux

WIREDTIGER_CONFIGURED=`ps -ef|grep mongod|grep -i storageengine|grep -ic wiredtiger`
echo ${WIREDTIGER_CONFIGURED}

1 means it's there

From the mongo shell

db.serverStatus()

You should see something like this

"wiredTiger" : {
   ...
   "cache" : {
      "tracked dirty bytes in the cache" : <num>,
      "bytes currently in the cache" : <num>,
      "maximum bytes configured" : <num>,
      "bytes read into cache" :<num>,

or you can just pull the storage engine name with

db.serverStatus().storageEngine.name

You will either get mmapv1 or wiredTiger

or from the command line

MONGO_ENGINE=`mongo -u... -p... --eval "db.serverStatus().storageEngine.name"`

Answer 3

The mongod.log file gets populated by a string which describes what storage engine you're using;
so you could run:

cat /var/log/mongodb/mongod.log  | grep STORAGE | tail -n 1

which returns something like:

2017-06-28T21:45:24.745+0200 I STORAGE  [initandlisten] wiredtiger_open config: create,cache_size=4G,session_max=20000,eviction=(threads_min=4,threads_max=4),config_base=false,statistics=(fast),log=(enabled=true,archive=true,path=journal,compressor=snappy),file_manager=(close_idle_time=100000),checkpoint=(wait=60,log_size=2GB),statistics_log=(wait=0),