IBM 86655RY Hardware Maintenance Manual - Page 223

pop-up window A box on the display screen that displays information or asks the user to make choices. POST Power-on self-test. RAID Redundant array of independent disks. RBL Rebuild. A drive in this state is being rebuilt. Only the IBM ServeRAID adapter has this state. RDY Ready. RDY appears as the status of a drive that the ServeRAID adapter detects as installed, spun up, but not configured in an array. redundancy In a functional unit, the existence of more than one means for performing a required function. RAID-0 RAID level-0 stripes the data across all of the drives of the array. RAID-0 offers substantial speed enhancement, but provides for no data redundancy. Therefore, a defective hard disk within the array results in loss of data in the logical drive assigned level-0, but only in that logical drive. RAID-1 RAID level-1 provides an enhanced feature for disk mirroring that stripes data as well as copies of the data across all the drives of the array. The first stripe is the data stripe, and the second stripe is the mirror (copy) of the first data stripe. The data in the mirror stripe is written on another drive. Because data is mirrored, the capacity of the logical drive when assigned level-1 is 50% of the physical capacity of the grouping of hard disk drives in the array. RAID-5 RAID level-5 stripes data and parity across all drives of the array. When a disk array is assigned RAID-5, the capacity of the logical drive is reduced by one physical drive size because of parity storage. The parity is spread across all drives in the array. If one drive fails, the data can be rebuilt. If more than one drive fails but one or none of the drives are actually defective, then data may not be lost. You can use a process called software replacement on the non-defective hard drives. SID SCSI ID. A zero based counting scheme (0, 1, ... 15) for the SCSI devices on a channel. SBY Standby. A standby drive is a hard disk drive that the ServeRAID adapter has spun down. Devices such as tape drives and CD-ROM drives are also considered to be in a standby state. Only the IBM ServeRAID adapter has the state. sector A predetermined angular part of a track or band on a magnetic disk that can be addressed. server In a network, a data station that provides facilities to other stations; for example, a file server, a print server, a mail server. stripe The collection of sectors, in logical order, from the first to the last drive of the disk array, over which data is stored. striping The process of storing data across all the drives grouped in an array. synchronize In a disk array, to compute and store the parity of all the data in the array. software replace Refers to when the hard disk drive is not physically replaced in the system. A drive may have been marked defunct but brought back online using . The drive is rebuilt without having been physically replaced. This could occur because, when the ServeRAID adapter communicates with the hard file and receives an unexpected response, the adapter marks the drive defunct to avoid any potential data loss. Installing and configuring ServeRAID controllers 213