CSC 4710 Lecture Notes - Lecture 16: Hard Disk Drive Performance Characteristics, Database, Transaction Processing
16 Dec 2019
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I/o time to access a page is under head (avg = ~5 - 10 ms) Large page size data related to x stored in same page; hence additional page transfer can be avoided. If a single request accesses data that is stored separately on different disks, that data can be transferred in parallel. If a file is to be stored on three disks. Level 1: striping but no redundancy: a striped array of n disks, the failure of a single disk ruins everything, raid levels (con"t) Level 2: mirrored disks (no striping: an array of n mirrored disks, all data stored on two disks. If one disk fails, the system can continue. Increases speed of reads: both of the mirrored disks can be read concurrently, decreases speed of writes, each write must be made to two disks, requires twice the number of disks, raid levels (con"t)
