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Chapter 3: Backup and RecoveryPerformance In a major disaster recovery, you have to first restore the files to disk, then execute thedatabase recovery from the files on disk.This process increases the time to recover the system.There are other options available for a faster backup, such as the various High Availabilityoptions, but these options are beyond the scope of this guidebook.The performance requirement for a recovery is more critical than for backup. Recoveryperformance determines how quickly the system will be available for use and how soonbusiness can continue. The goal is to restore the database and related files to make thesystem quickly available for general use. The longer this restore takes, the greater the impacton your business.To increase database restore performance, all of the above database backup options arevalid. The option also exists to restore to a faster disk array with a higher data-writethroughput.There are different ways to restore to a faster disk array: Dedicated drivesIn conjunction with parallel backups, restoring files and tablespaces to individuallydedicated disk drives makes the process faster. Because at any one time, only onetablespace or file is written to the drive, you do not have head contention writinganother tablespace to the same drive. RAID typeMirrored stripe (RAID 0+1) is faster than RAID5, but this speed depends on the specifichardware. In most cases, the task of computing the parity data for the parity drive(RAID5) takes more time than it would to write all the data twice (RAID 0+1). Thisoption is expensive because the usable capacity is 50 percent of the total raw capacity—significantly less than RAID5: RAID 0+1 = [single_drive_capacity × (number_of_drives/2)] RAID5 = [single_drive_capacity × (number of drives – 1)] Drives with faster write performance Drive array “system” with faster write performanceSystem Administration Made Easy3–23