HP 273914-B21 HP Smart Array Controller technology, 3rd edition - Page 17

HP worked with the disk drive industry to help develop a diagnostic and failure prediction capability known as Self-Monitoring Analysis and Reporting Technology (S.M.A.R.T.). Over the years, as S.M.A.R.T. matured, HP used both M&P and S.M.A.R.T. to support disk drive failure prediction technology for Pre-Failure Warranty disk drive replacement. S.M.A.R.T. has matured to the point that HP relies exclusively on this technology for disk drive failure prediction to support Pre-Failure Warranty. Since 1997, all HP SCSI, SAS, and SATA server-class disk drives have incorporated S.M.A.R.T. technology. S.M.A.R.T. disk drives have the capacity to inform the host when a disk drive is experiencing abnormal operation likely to lead to drive failure. S.M.A.R.T. improves failure prediction technology by placing monitoring capabilities within the disk disk drive. These monitoring routines are more accurate than the original M&P tests because they are designed for a specific drive type and have direct access to internal performance, calibration, and error measurements. S.M.A.R.T. uses internal performance indicators and real-time monitoring and analysis to improve data protection and fault prediction capability beyond that of the original M&P tests. In addition, HP Smart Array controllers proactively scan the disk drive media during idle time and repair, or report, any media defects detected. S.M.A.R.T. can often predict a problem before failure occurs. HP Smart Array controllers recognize S.M.A.R.T. error codes and notify HP Systems Insight Manager5 (SIM) whenever a potential problem arises. HP SIM, in turn, immediately notifies administrators of drive failures. The drive parameter tracking feature allows Smart Array controllers to warn of potential drive problems before they occur. HP drives that fail to meet the expected criteria may be eligible for replacement under the HP Pre-Failure Warranty. Automatic data recovery with rapid rebuild technology When a disk drive in an array is replaced, Smart Array controllers use the fault-tolerance information on the remaining drives in the array to reconstruct the missing data and write it to the replacement drive. This process is called automatic data recovery, or rebuild. If fault tolerance is compromised, the data cannot be reconstructed and is likely to be permanently lost. The latest generation of HP Smart Array controllers includes rapid rebuild technology for accelerating the rebuild process. Rapid rebuild technology comprises several features that result in substantially quicker rebuild time. Faster rebuild time reduces the risk of logical drive failure by restoring logical drives to full fault tolerance before a subsequent drive failure can occur. Generally, a rebuild operation requires approximately 15 to 30 seconds per gigabyte for RAID 5 or RAID 6. However, actual rebuild time depends on several factors, including the amount of I/O activity occurring during the rebuild operation, the number of disk drives in the logical drive, the rebuild priority setting, and the disk drive performance. The ACU allows administrators to view the rebuild progress and set the priority for the rebuild operation. Online spare Smart Array controllers enable administrators to designate an unlimited number of drives as online spares to arrays containing one or more fault-tolerant logical drives. The same spare drive can be assigned to multiple arrays as a global spare. Smart Array configuration utilities ensure that SAS disk drives can only be assigned as spares for SAS arrays (and likewise, SATA disk drives for SATA arrays). During system operation, these spare drives remain up and running but not active; that is, no I/O operations are performed to them during normal array operation. Spare drives are held in reserve in case one of the active drives in the array fails, and then an online spare drive is selected as the replacement disk drive. 5 For a more detailed discussion of HP Systems Insight Manager, refer to the "HP Systems Insight Manager" section. 17