COSI 127b Study Guide - Final Guide: Nested Raid Levels, Standard Raid Levels
27 Apr 2020
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Document Summary
Raid 10 is faster than raid 1, but is has the same cost. Raid 3 uses block striping with a dedicated parity drive. Parity requires fewer disks but is less reliable than mirroring. Raid 5 is block striping with distributed parity. A buffer is an area of process space where data resides before and after disk access. The buffer manager can clear space in the buffer by using a page replacement policy. Databases often know what blocks will next be needed. Thus, the query processor can provide hints to the buffer manager. Therefore, databases can do better at avoiding disk accesses than operating systems. A file is a sequence of records, and a record is a sequence of fields. Files are stored as a collection of blocks (a unit of disk access). Representing tuples with fixed length records has good compactness (only the data is being stored), but bad delete/insert overhead.
