Overflow to Disk

This examples demonstrates how to use GemFire’s Overflow to disk.

In this example, a server hosts a partitioned region that stores strings. The example shows entry values being overflowed to disk and removed from memory.

This example assumes that GemFire is installed.

Set up the region

1. Set directory gemfire-examples/overflow to be the current working directory. Each step in this example specifies paths relative to that directory.

2. Run a script that starts a locator and two servers. The script then creates the example-region region and puts 4 entries.

    $ gfsh run --file=scripts/start.gfsh
   

Note that both the region size and totalEntriesOnlyOnDisk are 0 before we put any entries.

3. Shut down the cluster

    $ gfsh run --file=scripts/stop.gfsh
   

4. In the output of the second show metrics --region=example-region command, notice the line

diskstore | totalEntriesOnlyOnDisk | 2

This shows that 2 values have been overflowed to disk and are no longer in memory. Notice that the size from the second describe region --name=example-region is still 4

Region | size | 4

Because all the keys remain in memory. The entries are still accessible.