Metadata management for fixed content distributed data storage

C \NRPonh\DCC\KXM\41)6 1691_ 1 DOC-20/12/2011 An archival storage cluster of preferably symmetric nodes includes a metadata management system that organizes and provides access to given metadata, preferably in 5 the form of metadata objects. Each metadata object may have a unique name, and metadata objects are organized into regions. Preferably, a region is selected by hashing one or more object attributes (e.g., the object's name) and extracting a given number of bits of the resulting hash value. The number of bits may be controlled by a configuration parameter. Each region is stored redundantly. A region comprises a set of region copies. In particular, 10 there is one authoritative copy of the region, and zero or more backup copies. The number of backup copies may be controlled by a configuration parameter. Region copies are distributed across the nodes of the cluster so as to balance the number of authoritative region copies per node, as well as the number of total region copies per node. Backup region copies are maintained synchronized to their associated authoritative region copy. WO 2006/015097 PCT/US2005/026747 Region map 420 JVM 412 402a 404 MMC 406 .400- DB -- 41a IRegion map Figure 4 RegloN Autfiodtiaive Backup 1 Backup 2 0 n1 n2 n3 1 n2 n3 n 2 n3 n4 n1 3 n4 n1 n2 4 n1 n2 n3 63 n4 n1 n2 Figure 5 606 608 610 612 614 616 t 618 \ 00 01 /0 11 /~a 1o I \ \ io 622 624 626 628 Figure 6