Expert Oracle Exadata - Parent Directory

CHAPTER 9 RECOVERING EXADATAPoor PerformanceIf a disk exhibits poor performance, it should be replaced. A single poorly performing cell disk canimpact the performance of other healthy disks. When a disk begins performing extremely badly, itsstatus will be set to Poor Performance. As is the case with Predictive Failure status, ASM willautomatically drop all grid disks (on this cell disk) from the disk groups and begin a rebalance operation.Once the rebalance is complete you can remove and replace the failing disk drive. You can use theCellCLI command CALIBRATE to manually check the performance of all disks in the storage cell. Thefollowing listing shows the output of the CALIBRATE command. Ordinarily, cellsrv should be shut downbefore running CALIBRATE, because it can significantly impact I/O performance for databases using thestorage cell. If you cannot shut down cellsrv for the test, you can run CALIBRATE using the FORCE option.As daunting as that sounds, FORCE simply overrides the safety switch and allows you to run CALIBRATEwhile cellsrv is up and applications are using the cell disks. The following listing shows the output fromthe CALIBRATE command run on a healthy set of cell disks:CellCLI> calibrateCalibration will take a few minutes...Aggregate random read throughput across all hard disk luns: 1025 MBPSAggregate random read throughput across all flash disk luns: 3899.18 MBPSAggregate random read IOs per second (IOPS) across all hard disk luns: 1707Aggregate random read IOs per second (IOPS) across all flash disk luns: 145158Controller read throughput: 1245.08 MBPSCalibrating hard disks (read only) ...Lun 0_0 on drive [35:0 ] random read throughput: 83.80 MBPS, and 144 IOPSLun 0_1 on drive [35:1 ] random read throughput: 87.85 MBPS, and 145 IOPSLun 0_10 on drive [35:10 ] random read throughput: 91.23 MBPS, and 145 IOPSLun 0_11 on drive [35:11 ] random read throughput: 91.32 MBPS, and 150 IOPSLun 0_2 on drive [35:2 ] random read throughput: 92.07 MBPS, and 147 IOPSLun 0_3 on drive [35:3 ] random read throughput: 91.59 MBPS, and 150 IOPSLun 0_4 on drive [35:4 ] random read throughput: 93.71 MBPS, and 149 IOPSLun 0_5 on drive [35:5 ] random read throughput: 89.86 MBPS, and 147 IOPSLun 0_6 on drive [35:6 ] random read throughput: 91.65 MBPS, and 148 IOPSLun 0_7 on drive [35:7 ] random read throughput: 88.06 MBPS, and 145 IOPSLun 0_8 on drive [35:8 ] random read throughput: 91.00 MBPS, and 149 IOPSLun 0_9 on drive [35:9 ] random read throughput: 90.81 MBPS, and 149 IOPSCalibrating flash disks (read only, note that writes will be significantly slower) ...Lun 1_0 on drive [[2:0:0:0]] random read throughput: 242.51 MBPS, and 19035 IOPSLun 1_1 on drive [[2:0:1:0]] random read throughput: 240.89 MBPS, and 19018 IOPSLun 1_2 on drive [[2:0:2:0]] random read throughput: 240.90 MBPS, and 19111 IOPSLun 1_3 on drive [[2:0:3:0]] random read throughput: 241.62 MBPS, and 18923 IOPSLun 2_0 on drive [[4:0:0:0]] random read throughput: 242.08 MBPS, and 19066 IOPSLun 2_1 on drive [[4:0:1:0]] random read throughput: 251.11 MBPS, and 19263 IOPSLun 2_2 on drive [[4:0:2:0]] random read throughput: 245.65 MBPS, and 19119 IOPSLun 2_3 on drive [[4:0:3:0]] random read throughput: 247.83 MBPS, and 19139 IOPSLun 4_0 on drive [[1:0:0:0]] random read throughput: 250.36 MBPS, and 19036 IOPSLun 4_1 on drive [[1:0:1:0]] random read throughput: 249.82 MBPS, and 19006 IOPSLun 4_2 on drive [[1:0:2:0]] random read throughput: 252.82 MBPS, and 19140 IOPSLun 4_3 on drive [[1:0:3:0]] random read throughput: 250.80 MBPS, and 18979 IOPSLun 5_0 on drive [[3:0:0:0]] random read throughput: 253.21 MBPS, and 19167 IOPSLun 5_1 on drive [[3:0:1:0]] random read throughput: 252.01 MBPS, and 19152 IOPSLun 5_2 on drive [[3:0:2:0]] random read throughput: 251.86 MBPS, and 19160 IOPSLun 5_3 on drive [[3:0:3:0]] random read throughput: 244.24 MBPS, and 18925 IOPS312