In Couchbase Server 2.0, we provide a more optimized disk warmup. In past versions of Couchbase Server, the server would load all keys and data sequentially from vBuckets in RAM. Now the server pre-fetches a list of most-frequently accessed keys and fetches these documents first. The server runs a periodic scanner process which will determine which keys are most frequently-used. You can use cbepctl flush_param to change the initial time and the interval for the process. You may want to do this, for instance, if you have a peak time for your application when you want the keys used during this time to be quickly available after server restart.

Be aware that this tool is a per-node, per-bucket operation. That means that if you want to perform this operation, you must specify the IP address of a node in the cluster and a named bucket. If you do not provided a named bucket, the server will apply the setting to any default bucket that exists at the specified node. If you want to perform this operation for an entire cluster, you will need to perform the command for every node/bucket combination that exists for that cluster.

By default the scanner process will run once every 24 hours with a default initial start time of 2:00 AM UTC. This means after you install a new Couchbase Server 2.0 instance or restart the server, by default the scanner will run every 24- hour time period at 2:00 AM GMT and then 2:00 PM GMT by default. To change the time interval when the access scanner process runs to every 20 minutes:

shell> ./cbepctl hostname:port -b bucket1 -p bucket_password set flush_param alog_sleep_time 20

To change the initial time that the access scanner process runs from the default of 2:00 AM UTC:

shell> ./cbepctl hostname:port -b bucket1 -p bucket_password set flush_param alog_task_time 23

In this example we set the initial time to 11:00 PM UTC.