When working with an Oracle Exadata appliance you normally do not have to come close to the machine itself as with most servers. However in some cases a disk will be faulty and is in need of replacement. The Oracle exadata, depending on what "size" you have, will have a number of storage nodes available in the rack. Each node will have a number of disks in it. When you need to replace a broken disk with a new disk it can be quite handy to ensure you are removing the correct faulty disk and not a disk which is perfectly fine. To help the people who will do the physical swapping of the disk there is a Service LED located on each disk which you can turn on or off. This will help the engineer to locate the correct disk without having the need to count disks and nodes.
To turn on, or to turn off, the Service LED on a disk you have to make use of the CellCLI. For example we are in need of turning the Sevice LED on for 3 disks we will use the following command:
CellCLI> alter physicaldisk 32:0,32:1,32:2 serviceled on
To disable the Service LED we use the following command:
CellCLI> alter physicaldisk 32:0,32:1,32:2 serviceled off