Google Inc.

Michael O'Reilly

Alexandre Drobychev

Alexander Kesselman

George Datuashvili

Dmitry Broyde

Mark Waldron

Angus Lees

A location assignment daemon (LAD) manages placement of object replicas in a distributed storage system. The distributed storage system may include a plurality of instances, which may be at distinct geographic locations. The LAD determines placement categories for objects stored in the distributed storage system. A placement category for an object corresponds to the object's placement policy and current replica locations. There are substantially fewer placement categories than objects. The LAD determines an action plan for each placement category whose associated objects require either creation or removal of object replicas. Each action plan includes either creating or removing an object replica. The LAD prioritizes the action plans and implements at least a subset of the action plans in priority order in accordance with available resources in the distributed storage system. Each action plan is applied to objects in the placement category corresponding to the action plan.

Categorization for constraint-based placement of object replicas in a distributed storage system

Placement of object replicas in a distributed storage system includes, at a first instance, opening a journal for storage of object chunks. An object is received, which comprises one or more chunks. Each chunk comprises one or more storage blocks. The blocks for a single chunk are stored in a single journal. Global metadata for the object is stored, which includes a list of chunks for the object. Local metadata for the chunk is stored, which includes a block list identifying each block of the plurality of blocks. The local metadata is associated with the journal. The journal is later closed. The journal is subsequently replicated to a second instance. The global metadata is updated to reflect the replication, whereas the local metadata is unchanged by the replication.

Hierarchical chunking of objects in a distributed storage system

A system, computer-readable storage medium storing at least one program, and a computer-implemented method for storing metadata for a file in a distributed storage system is presented. Metadata for a file is generated. A subset of metadata clusters in a distributed storage system is identified to form a quorum of metadata clusters. Requests to store the metadata for the file on the metadata clusters in the distributed storage system are issued, where the requests include high priority requests to store the metadata for the file on at least one of the metadata clusters in the quorum of metadata clusters and normal priority requests to store the metadata in the remaining metadata clusters, the metadata being stored on the at least one of the metadata clusters in the quorum of metadata clusters before being stored on the remaining metadata clusters.

System and method for storing metadata for a file in a distributed storage system

Placement of object replicas in a distributed storage system includes, at a first instance, opening a journal for storage of object chunks. Each journal is associated with a single placement policy. An object is received, which comprises a chunk. The object has a placement policy, and the chunk comprises a plurality of storage blocks. The blocks are stored in a journal that matches the placement policy. Global metadata for the object is stored, which includes a list of chunks for the object. Local metadata for the chunk is stored, which includes a block list identifying each block of the plurality of blocks. The local metadata is associated with the journal. The journal is later closed. The journal is subsequently replicated to a second instance according to the placement policy. The global metadata is updated to reflect the replication, whereas the local metadata is unchanged by the replication.

In one implementation, groups of objects may be maintained, each group including one or more objects that are to be replicated at one or more of the storage clusters. The objects may be assigned to the groups based on replication choices where at least some of the objects are assigned to multiple ones of the groups. A priority value may be determined and associated with each of the groups, the priority value of a particular group being determined based on priority values associated with objects within the particular group. The objects may be selected, for replication, in a replication order based on the priority value of the groups and replication of the selected objects may be initiated.

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Michael O'Reilly