Reference count propagation

• US 8,898,195 B2
• Filed: 12/21/2012
• Issued: 11/25/2014
• Est. Priority Date: 05/13/2011
• Status: Expired due to Fees

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: SimpliVity Corporation (Hewlett-Packard Enterprise Company)
• Inventors: Beaverson, Arthur J., Chitrapu, Kishore, Czerkowicz, John Michael, Manjanatha, Sowmya
• Primary Examiner(s): Woo, Issac M
• Application Number:
  US13/723,990
• Publication Number:
  US 20130110894A1
• Time in Patent Office: 704 Days
• Field of Search: 707600-899
• US Class Current: 707/791
• CPC Class Codes: G06F 16/134 Distributed indices
• CPC Class Codes: G06F 16/137 Hash-based content-based indexing of textual data G06F16/31
• CPC Class Codes: G06F 16/182 Distributed file systems
• CPC Class Codes: H04L 67/1087 using cross-functional networking aspects

Abstract

Methods and systems are provided for tracking object instances stored on a plurality of network nodes, which tracking enables a global determination of when an object has no references across the networked nodes and can be safely de-allocated. According to one aspect of the invention, each node has a local object store for tracking and optionally storing objects on the node, and the local object stores collectively share the locally stored instances of the objects across the network. One or more applications, e.g., a file system and/or a storage system, use the local object stores for storing all persistent data of the application as objects.

Claims

1. A non-transitory computer-readable medium containing executable program instructions for performing a method comprising:

in a plurality of networked nodes wherein each node has a local object store, the local object stores storing objects and sharing one or more objects, the objects having globally unique names across the networked nodes and wherein the object names do not change based upon where the objects are stored on the nodes;

maintaining, at each node, a Local Reference Count LRC of local references to object names, independent of any object instance stored in the local object store, the LRC being maintained as a signed integer, wherein adjustments are made to the LRC for each local new reference and dereference and a de-referencing of an object name can generate a negative LRC value;

wherein ownership of object names are assigned to different nodes, a range of object names being assigned to one of the network nodes and the node assigned ownership initiates a Global Reference Count GRC determining step for all or a subset of the range, the GRC determining step comprising;

the owner node providing a unique tag for an object for which a GRC is to be determined;

the nodes exchanging messages with the unique tag, whereby, the other nodes provide the owner node with their LRC for the object;

the owner node calculating the GRC as a sum of the LRCs received from the other nodes and the LRC of the owner node for the object; and

if the resulting GRC is zero the owner node sending a delete message with the unique tag to the other nodes.

2. The medium of claim 1, wherein the method includes:

the owner and other nodes delete the object when the GRC is zero.

3. The medium of claim 2, wherein the determining step includes:

the nodes operate as a peer-to-peer network of nodes.

4. The medium of claim 3, wherein

the GRC is calculated while the objects are being read or written and local object reference counts are being modified.

5. The medium of claim 1, wherein the local object stores collectively comprise a namespace of the globally unique object names.

6. The medium of claim 1, wherein the method includes:

the local object store maintains a local mapping index of object name, LRC and a pointer to any physical object location where the object is stored on the local object store.

7. The medium of claim 1, wherein the method includes:

each object has an object fingerprint derived from the object'"'"'s content as its object name.

8. The medium of claim 7, wherein the method includes:

the fingerprint comprises a hash of the object content.

9. The medium of claim 1, wherein a file system uses the local object stores collectively as a method to store all persistent data of the file system.

10. The medium of claim 9, wherein the method includes:

all file system data, metadata and files comprise objects of the object store(s), each object having an object fingerprint as the object name;

collections of file system objects also comprise objects of the object store(s), each collection comprising a mapping of a plurality of the file system objects and having a collection object fingerprint derived from the contents of the collection, wherein a change to one or more objects of the collection changes the collection object fingerprint; and

a file system root object having a root object fingerprint derived from all of the objects of the file system, such that every object in the namespace file system is accessible through the root object.

11. The medium of claim 1, wherein the method includes:

selecting, based on network or system performance or reliability, one or more of the nodes as location(s) for storing one or more instances of an object independent of the object name.

12. The medium of claim 1, wherein the method includes:

the sharing of the stored objects comprises communicating between nodes with regard to object names, LRCs and locations of stored objects.

13. The medium of claim 1, wherein the method includes:

when an application de-references an object name and a copy of the object is not stored on a local node, the local node generates an LRC of negative one.

14. The medium of claim 1, wherein

a storage system uses the local object stores collectively as a method to store all persistent data of the storage system.

15. An apparatus comprising:

a plurality of networked nodes, each node having a local object store for storing objects on the respective node and the objects having globally unique names across the networked nodes, wherein the object names do not change based upon where the objects are stored on the nodes;

the local object stores sharing one or more of the objects;

an application using the local object stores for storing persistent data as objects, the application requiring a reference count for each object stored on the networked nodes comprising a number of independent paths across the plurality of nodes to the respective object;

means for maintaining a local reference count LRC of references to object names on each node independent of any object instance stored in the local object store, the LRC being maintained as a signed integer;

wherein adjustments are made to the LRC for each local new reference and dereference, wherein a de-referencing of an object name can generate a negative LRC value; and

means for determining a Global Reference Count GRC for an object, wherein ownership of object names are assigned to different nodes, a range of object names being assigned to one of the network nodes, and the node assigned ownership is configured to cause the determining means to initiate a GRC determining step for all or a subset of the range, the GRC determining means and the nodes configured to implement GRC determining steps comprising;

the owner node providing a unique tag for an object for which a GRC is to be determined;

the nodes exchanging messages with the unique tag, whereby, the other nodes provide the owner node with their LRC for the object;

the owner node calculating the GRC as a sum of the LRCs received from the other nodes and the LRC of the owner node for the object; and

if the resulting GRC is zero the owner node sending a delete message with the unique tag to the other nodes.