Managing global cache coherency in a distributed shared caching for clustered file systems

• US 9,251,075 B2
• Filed: 04/29/2014
• Issued: 02/02/2016
• Est. Priority Date: 08/25/2008
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Aronovich, Lior, Toaff, Yair, Paz, Gil, Asher, Ron
• Primary Examiner(s): Casanova, Jorge A
• Application Number:
  US14/264,944
• Publication Number:
  US 20140236998A1
• Time in Patent Office: 644 Days
• Field of Search: 707/781, 707/826
• US Class Current: 1/1
• CPC Class Codes: G06F 12/0802 Addressing of a memory level in which the access to the desired data or data block requires associative addressing means, e.g. caches
• CPC Class Codes: G06F 12/0815 Cache consistency protocols
• CPC Class Codes: G06F 12/0828 with concurrent directory accessing, i.e. handling multiple concurrent coherency transactions
• CPC Class Codes: G06F 12/084 with a shared cache
• CPC Class Codes: G06F 16/11 File system administration, e.g. details of archiving or snapshots file system backup G06F11/14
• CPC Class Codes: G06F 16/13 File access structures, e.g. distributed indices arrangements of input from, or output to, record carriers G06F3/06
• CPC Class Codes: G06F 16/16 File or folder operations, e.g. details of user interfaces specifically adapted to file systems
• CPC Class Codes: G06F 16/172 Caching, prefetching or hoarding of files
• CPC Class Codes: G06F 16/182 Distributed file systems
• CPC Class Codes: G06F 16/183 Provision of network file services by network file servers, e.g. by using NFS, CIFS network file access protocols H04L67/1097
• CPC Class Codes: G06F 16/1865 Transactional file systems
• CPC Class Codes: G06F 16/24552 Database cache management
• CPC Class Codes: G06F 21/6218 to a system of files or objects, e.g. local or distributed file system or database
• CPC Class Codes: G06F 2212/604 Details relating to cache allocation

Abstract

Various embodiments are provided for managing a global cache coherency in a distributed shared caching for a clustered file system (CFS). The CFS manages access permissions to an entire space of data segments by using the DSM module. In response to receiving a request to access one of the data segments, a calculation operation is performed for obtaining most recent contents of one of the data segments. The calculation operation performs one of providing the most recent contents via communication with a remote DSM module which obtains the one of the data segments from an associated external cache memory, instructing by the DSM module to read from storage the one of the data segments, and determining that any existing contents of the one of the data segments in the local external cache are the most recent contents.

Claims

1. A method for managing global cache coherency in a distributed shared caching for clustered file systems (CFS) in a computing environment, the method comprising:

providing the CFS for residing on a cluster of nodes for accessing space of data segments that are shared between the cluster of nodes;

providing, in the CFS, a local cache memory of data segment slots on each of the cluster of nodes and a distributed shared memory (DSM) module, with no internal memory for the data segments on each of the cluster of nodes, wherein the cache memory acts as an external memory; and

managing access permissions to an entire space of the data segments by using the DSM module, wherein in response to receiving a request to access one of the data segments;

performing a calculation operation for obtaining most recent contents of the one of the data segments, wherein the calculation operation performs one of;

providing the most recent contents via communication with a remote DSM module which obtains the one of the data segments from an associated external cache memory,

instructing by the DSM module to read from storage the one of the data segments, and

determining that any existing contents of the one of the data segments in the local external cache are the most recent contents;

wherein if ownership of the one of the data segments is possessed by a remote DSM module and a condition of the request to access one of the data segments is for shared permission and a current permission on the one of the data segments is shared and the one of the data segments exists in the local external cache does not exist;

sending a response for the request to access one of the data segments to a remote DSM module; and

transporting the most recent contents of the one of the data segments within the response if the response is in a remote external cache and has a valid permission for the one of the data segments otherwise reading from the one of the data segments.

2. The method of claim 1, further including reading from the one of the data segments if one of the DSM module instructs to read from the one of the data segments, or if any of the contents of the one of the data segments are the most recent contents, and the one of the data segments is not present in the local external cache.

3. The method of claim 1, further including reading from the one of the data segments if ownership of the one of the data segments is possessed by a local DSM module and there is no valid permission on the one of the data segments.

4. The method of claim 1, further including determining contents of the one of the data segments are the most recent contents if ownership of the one of the data segments is possessed by a local DSM module and there is a valid permission on the one of the data segments.

5. The method of claim 1, further including determining contents of the one of the data segments are the most recent contents if ownership of the one of the data segments is possessed by a remote DSM module and the request to access one of the data segments is for shared permission and a current permission on the one of the data segments is shared and the one of the data segments exists in the local external cache.

6. A system for managing global cache coherency in a distributed shared caching for clustered file systems (CFS) in a computing environment, the system comprising:

a cluster of nodes,

the CFS including the cluster of nodes forming a computer cluster,

data segments shared between the cluster of nodes, wherein the CFS resides on the cluster of nodes for accessing space of data segments that are shared between the cluster of nodes,

a distributed shared memory (DSM) module, with no internal memory for the data segments on each of the cluster of nodes within a node of the cluster of nodes;

a plurality of storage devices in communication with the CFS,

a local cache memory of data segment slots on each of the cluster of nodes, wherein the cache memory acts as an external memory,

a remote cache memory within each of the cluster of nodes,

a cache associated with the node, and

a processor device having a memory coupled to the processor device for controlling the CFS, wherein the processor device is assigned to the node and the node is in communication with the plurality of storage devices, wherein the processor device;

manages access permissions to an entire space of the data segments by using the DSM module, wherein in response to receiving a request to access one of the data segments;

performs a calculation operation for obtaining most recent contents of the one of the data segments, wherein the calculation operation performs one of;

 

provides the most recent contents via communication with a remote DSM module which obtains the one of the data segments from an associated external cache memory,

 

instructs by the DSM module to read from a storage device the one of the data segments, and

 

determines that any existing contents of the one of the data segments in the local external cache are the most recent contents;

if ownership of the one of the data segments is possessed by a remote DSM module and a condition of the request to access one of the data segments is for shared permission and a current permission on the one of the data segments is shared and the one of the data segments exists in the local external cache does not exist;

sends a response for the request to access one of the data segments to a remote DSM module; and

transports the most recent contents of the one of the data segments within the response if the response is in a remote external cache and has a valid permission for the one of the data segments otherwise reading from the one of the data segments.

7. The system of claim 6, wherein the processor device reads from the one of the data segments if one of the DSM module instructs to read from the one of the data segments, if any of the contents of the one of the data segments are the most recent contents, and the one of the data segments is not present in the local external cache.

8. The system of claim 6, wherein the processor device reads from the one of the data segments if ownership of the one of the data segments is possessed by a local DSM module and there is no valid permission on the one of the data segments.

9. The system of claim 6, wherein the processor device determines contents of the one of the data segments are the most recent contents if ownership of the one of the data segments is possessed by a local DSM module and there is a valid permission on the one of the data segments.

10. The system of claim 6, wherein the processor device determines contents of the one of the data segments are the most recent contents if ownership of the one of the data segments is possessed by a remote DSM module and the request to access one of the data segments is for shared permission and a current permission on the one of the data segments is shared and the one of the data segments exists in the local external cache.

11. A computer program product for managing a global cache coherency in a distributed shared caching for clustered file systems (CFS) using a processor device, the computer program product comprising a non-transitory computer-readable storage medium having computer-readable program code portions stored therein, the computer-readable program code portions comprising:

a first executable portion that provides the CFS for residing on a cluster of nodes for accessing space of data segments that are shared between the cluster of nodes;

a second executable portion that provides, in the CFS, a local cache memory of data segment slots on each of the cluster of nodes and a distributed shared memory (DSM) module, with no internal memory for the data segments on each of the cluster of nodes, wherein the cache memory acts as an external memory; and

a third executable portion that manages access permissions to an entire space of the data segments by using the DSM module, wherein in response to receiving a request to access one of the data segments;

performs a calculation operation for obtaining most recent contents of the one of the data segments, wherein the calculation operation performs one of;

provides the most recent contents via communication with a remote DSM module which obtains the one of the data segments from an associated external cache memory,

instructs by the DSM module to read from a storage device the one of the data segments, and

determines that any existing contents of the one of the data segments in the local external cache are the most recent contents; and

if ownership of the one of the data segments is possessed by a remote DSM module and a condition of the request to access one of the data segments is for shared permission and a current permission on the one of the data segments is shared and the one of the data segments exists in the local external cache does not exist;

sends a response for the request to access one of the data segments to a remote DSM module; and

a fourth executable portion that transports the most recent contents of the one of the data segments within the response if the response is in a remote external cache and has a valid ermission for the one of the data segments otherwise readin from the one of the data segments.

12. The computer program product of claim 11, further including a fifth executable portion that reads from the one of the data segments if one of the DSM module instructs to read from the one of the data segments, if any of the contents of the one of the data segments are the most recent contents, and the one of the data segments is not present in the local external cache.

13. The computer program product of claim 11, further including a fifth executable portion that reads from the one of the data segments if ownership of the one of the data segments is possessed by a local DSM module and there is no valid permission on the one of the data segments.

14. The computer program product of claim 11, further including a fifth executable portion that determines contents of the one of the data segments are the most recent contents if ownership of the one of the data segments is possessed by a local DSM module and there is a valid permission on the one of the data segments.

15. The computer program product of claim 11, further including a fifth executable portion that determines contents of the one of the data segments are the most recent contents if ownership of the one of the data segments is possessed by a remote DSM module and the request to access one of the data segments is for shared permission and a current permission on the one of the data segments is shared and the one of the data segments exists in the local external cache.