Expert Oracle Exadata - Parent Directory

CHAPTER 9 RECOVERING EXADATAyou should check the status of the disk to ensure that its status is Normal before using it. The disk statusmay be verified using the CellCLI command LIST PHYSICALDISK as shown here:CellCLI> list physicaldisk where diskType=HardDisk AND status=critical detailWhen a disk is replaced, the storage cell performs the following tasks automatically:• The disk firmware is updated to match the other disk drives in the storage cell.• The cell disk is re-created to match that of the disk it replaced.• The replacement cell disk is brought online (status set to Normal).• The grid disk (or grid disks) that were on the failed disk are re-created.• The grid disk status is set to Active.Once the replacement grid disks are set to Active, ASM automatically opens the disk and begins theresilvering process. All these tasks are handled automatically by Exadata, making disk replacement afairly painless process.When to Replace a Cell DiskDisk failure can occur abruptly, causing the disk to go offline immediately, or it can occur gradually,manifesting poor I/O performance. Storage cells are constantly monitoring the disk drives. Thismonitoring includes drive performance, in terms of both I/O and throughput, and SMART metrics suchas temperature, speed, and read/write errors. The goal is to provide early warning for disks that are likelyto fail before they actually do. When Exadata detects a problem, an alert is generated with specificinstructions on how to replace the disk. If the system has been configured for email notification thesealerts will be emailed to you automatically.In the previous section we walked through a simulated drive failure. Had this been an actual diskfailure, the procedure for replacing the disk would follow the same steps we used for the simulation. Butwhat happens when Exadata’s early warning system determines that a drive is likely to fail soon? WhenExadata detects drive problems it sets the physical disk status attribute accordingly. The followingCellCLI command displays the status of all disks in the storage cell.CellCLI> list physicaldisk attributes name, status where disktype = 'HardDisk'35:0 normal35:1 normal...35:11 normalTable 9-3 shows the various disk status values and what they mean.310