Verfahren und System zum Auswählen von Daten für Migration in einem hierarchischen Datenspeichersystem mit Frequenzverteilungstabellen

摘要

A hierarchic disk array data storage system (10) has multiple storage disks (12) that define a physical storage space (34) and a RAID management system (16) that maps the physical storage space (34) into two virtual storage spaces. A RAID-level virtual storage space (40) presents the physical storage space as mirror and parity RAID areas where the mirror RAID areas store data according to RAID Level 1 and the parity RAID areas store data according to RAID Level 5. An application-level virtual storage space (50) presents the physical storage space as multiple virtual blocks which can be associated with mirror and parity RAID areas. The RAID management system (16) migrates the virtual blocks between the mirror and parity RAID areas to optimize performance and reliability. To select virtual blocks for migration from mirror to parity RAID areas, a frequency distribution table (60) is created to characterize the virtual blocks according to a predetermined distribution criteria. A virtual block is selected by segmenting the frequency distribution table (60) to identify virtual blocks. The application-level virtual storage space (50) is searched until a virtual block that satisfies the selection criterion is located. The located virtual block is then migrated to the parity RAID area.