Expert Oracle Exadata - Parent Directory

CHAPTER 9 RECOVERING EXADATA■ Note: Notice that we use the dcli command to run the CellCLI command LIST GRIDDISK ATTRIBUTES oneach cell in the storage grid. Basically, dcli allows us to run a command concurrently on multiple nodes. Thecell_group parameter is a file containing a list of all of our storage cells.If the output from the LIST GRIDDISK command indicates it is safe to do so, we can test whathappens when we take one of the grid disks for our SCRATCH_DG disk group offline. For this test we willphysically remove the disk drive from the storage cell chassis. The test configuration will be as follows:• For this test we will create a new tablespace with one datafile. The datafile is set toautoextend so it will grow into the disk group as data is loaded.• Next, we’ll generate a considerable amount of data in the tablespace by creating alarge table; a couple of billion rows from DBA_SEGMENTS should do it.• While data is being loaded into the large table, we will physically remove the diskfrom the cell chassis.• Once the data is finished loading, we will reinstall the disk and observe Exadata’sautomated disk recovery in action.The first order of business is to identify the location of the disk drive within the storage cell. To dothis we will use the grid disk name to find the cell disk it resides on, then we’ll use the cell disk name tofind the slot address of the disk drive within the storage cell. Once we have the slot address we will turnon the service LED on the front panel so we know which disk to remove.From storage cell 3, we can use the LIST GRIDDISK command to find the name of the cell disk we arelooking for:CellCLI> list griddisk attributes name, celldisk where name like 'SCRATCH.*' detailname:SCRATCH_DG_CD_05_cell03cellDisk:CD_05_cell03Now that we have the cell disk name, we can use the LIST LUN command to find the slot address ofthe physical disk we want to remove. In the following listing we see the slot address we’re looking for,16:5.CellCLI> list LUN attributes celldisk, physicaldrives where celldisk=CD_05_cell03 detailcellDisk:CD_05_cell03physicalDrives: 16:5With the slot address, we can use the MegaCli64 command to activate the drive’s service LED on thefront panel of the storage cell. Note that the \ characters in the MegaCli64 command below are used toprevent the Bash shell from interpreting the brackets ([]) around the physical drive address. (Singlequotes work as well, by the way.)/opt/MegaRAID/MegaCli/MegaCli64 -pdlocate -physdrv \[16:5\] -a0The amber LED on the front of the disk drive should be flashing as can be seen in Figure 9-2.306