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|1. (WO2018052780) HIERARCHICAL FAULT TOLERANCE IN SYSTEM STORAGE|
|Applicants:||ORACLE INTERNATIONAL CORPORATION
|Inventors:||MAHESHWAR, Mahanteshwar Chimangala
CHIEN, Hanlin Daniel
BAGAL, Prasad V.
|Title:||HIERARCHICAL FAULT TOLERANCE IN SYSTEM STORAGE|
Embodiments enable a database management system (DBMS) to manage two levels of disk failure groups. These two levels of redundancy are achieved by grouping the disks of the disk group for the DBMS into two levels of failure groups (i.e., "data sites" each containing two or more "failure groups" of disks). This system of disk grouping allows a DBMS to potentially tolerate the loss of both an entire first site and part of a second site. Such a DBMS uses a multi-level voting system, based on both failure group-level votes and site-level votes, to identify the current version of administrative data structures (ADS) that store key administrative data. In addition to data sites that store database data, the DBMS includes a quorum site with a single quorum failure group that stores a copy of the ADS. The quorum site contributes a site-level vote during a multi-level voting event.