Methods and apparatus facilitating access to shared storage among multiple computers

• US 7,584,222 B1
• Filed: 04/26/2005
• Issued: 09/01/2009
• Est. Priority Date: 06/01/2004
• Status: Active Grant

• Current Assignee: Citrix Systems, Inc. (Cloud Software Group)
• Original Assignee: Sanbolic, Inc. (Cloud Software Group)
• Inventors: Georgiev, Ivan I.
• Primary Examiner(s): Wu; Yicun
• Application Number:
  US11/114,905
• Time in Patent Office: 1,589 Days
• Field of Search: 707 8- 10, 707/200
• US Class Current: 1/1
• CPC Class Codes: G06F 11/1471 involving logging of persistent data for recovery
• CPC Class Codes: G06F 11/203 using migration
• CPC Class Codes: G06F 12/0804 with main memory updating G06F12/0806 takes precedence
• CPC Class Codes: G06F 12/084 with a shared cache
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache
• 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: Y10S 707/99931 Database or file accessing
• CPC Class Codes: Y10S 707/99938 Concurrency, e.g. lock management in shared database
• CPC Class Codes: Y10S 707/99939 Privileged access
• CPC Class Codes: Y10S 707/99952 Coherency, e.g. same view to multiple users
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

Each of multiple computers in a cluster of computers negotiates access to locations in a common storage system. Each of the computers (coupled together via a network) in the cluster includes a transaction manager application to coordinate access to shared storage locations (such as a volume or portions thereof) in the storage system. The transaction managers at each of the multiple computers utilize a unified address space that maps locations in the storage system to corresponding access properties maintained by respective transaction managers in the computers. The access properties derived from use of the unified address space indicate an access status of the regions or locations in the shared storage system. If necessary, the computers in a cluster communicate with each other to negotiate access to the shared storage. Also, the computers in a cluster communicate so that current access properties maintained in each computer are consistent.

Claims

1. A computer-implemented method for providing a plurality of processes concurrent access to shared storage, the method comprising:

at each of multiple computers having access to the shared storage, maintaining a unified address space that maps locations of the shared storage to corresponding data access information, the corresponding data access information indicating access rights granted to the multiple computers for accessing different portions of the shared storage;

receiving, from the plurality of processes, corresponding requests for access to a common location in the shared storage; and

processing the corresponding requests received from the plurality of processes by utilizing the unified address space to map the requests into the data access information and identify, at respective computers, access properties associated with the common storage location to identify possible contention issues associated with other processes having access to the common location in the shared storage;

at a given computer of the multiple computers;

receiving a request to access a file in the shared storage;

converting an identifier associated with the file to an address value in the unified address space;

mapping the address value in the unified address space to a pointer, the pointer pointing to specific data access information specifying access rights for the file; and

utilizing the pointer to obtain the specific data access information to determine which, if any, of the multiple computers has current access rights to the file in shared storage, the method further comprising;

accessing a property object in the specific data access information, the property object corresponding to the address value in the unified address space, the property object associated with a range starting at the address value in the unified address space to identify a current status of access rights of file data with respect to other computers having access to portions of the shared storage, the property object specifying access rights for a portion of shared storage;

utilizing the property object to identify a current status of access rights of file data with respect to other computers and their current accessibility rights with respect to a common volume in the shared storage.

2. The computer-implemented method as in claim 1 further comprising:

at a first computer of the multiple computers, receiving a message from a second computer of the multiple computers, the message including a request to modify specified data in the shared storage; and

at the first computer receiving the request, initiating modification of the specified data in the shared storage on behalf of the second computer alleviating a need for the second computer to modify the shared storage.

3. In an environment including multiple computers having concurrent access to shared storage, a computer-implemented method comprising:

providing a transaction manager at each of the multiple computers in the environment to coordinate access to locations in the shared storage, the transaction manager at each of the multiple computers utilizing a unified address space that maps locations in the shared storage to corresponding access properties maintained by respective transaction managers, the access properties indicating an access status of the locations associated with the shared storage, the transaction managers at each of the multiple computers supporting operations of;

receiving a request to access data stored in the shared storage;

identifying a unique address in a unified address space associated with the data stored in the shared storage;

utilizing the unique address to retrieve access properties associated with the data in the shared storage; and

based on the retrieved access properties, identifying whether other computers in the environment have requested contemporaneous access to the data and, if so, communicating with transaction managers at the other computers accessing a common storage location of the shared storage to resolve conflicts associated with multiple computers attempting to access the common storage location of the shared storage;

at each of the multiple computers;

maintaining the unified address space to span a range of address values, each of the address values corresponding to respective storage capacity in the shared storage;

producing boundaries within the unified address space; and

utilizing the boundaries to define ranges in the unified address space, the ranges in the unified address space representing corresponding portions of storage capacity in the shared storage;

maintaining a respective property object for each of the ranges in the unified address space, each respective property object indicating access rights to a respective portion of the shared storage to which a range pertains;

at a first computer of the multiple computers, receiving a request to access a file in the shared storage;

converting an identifier associated with the file to an address value in the unified address space;

based on the address value in the unified address space, identifying a specific range in the unified address space in which the address value resides;

accessing a property object for the specific range in the unified address space; and

analyzing the property object to identify which, if any, of the multiple computers has current access rights to the file.

4. A computer-implemented method as in claim 3 further comprising:

maintaining portions of the shared storage as multiple streams of data; and

utilizing the unified address space to perform coordinated operations among the multiple computers on the streams of data.

5. A computer-implemented method as in claim 3 further comprising:

maintaining access right properties local to each of the multiple computers for the streams of data residing in the shared storage, the access right properties for one computer being consistent with other computers in a corresponding cluster.

6. A computer-implemented method as in claim 3 further comprising:

via use of property objects at the multiple computers, reserving access rights to portions of the shared storage.

7. A computer-implemented method as in claim 3 further comprising:

utilizing property objects in the unified address space to support memory mapping of regions in the shared storage.

8. A computer-implemented method as in claim 3 further comprising:

from a given one of the transaction managers in a cluster of multiple computers having access to a common volume in the shared storage, negotiating with other computers in the cluster to obtain access rights for accessing a location in the shared storage.

9. A computer-implemented method as in claim 3 further comprising:

maintaining cluster time among the multiple computers, the cluster time of each computer being based on an ever growing function that increments one unit based on occurrence of each local event, the cluster time being maximized with respective remote cluster times of received messages.

10. A computer-implemented method as in claim 3 further comprising:

enabling exclusive access permissions among the multiple computers based on their corresponding gravities, wherein each of the gravities identifies a relative weighting of priority for ordered performing of transactions associated with a corresponding computer.

11. A computer-implemented method as in claim 3 further comprising:

enabling an older transaction within the multiple computers in a cluster to steal access rights of a younger transaction for a given location in the shared storage.

12. A computer-implemented method as in claim 3 further comprising:

in a cluster including the multiple computers, waiting for an older transaction to complete before performing a younger transaction for a common area of the shared storage.

13. A computer-implemented method as in claim 3 further comprising:

enabling exclusive access permissions among the multiple computers based on their corresponding gravities, wherein each of the gravities identifies a relative weighting of priority for performing transactions associated with a corresponding computer; and

if corresponding gravities of two conflicting computers attempting access to a common location in shared storage are identical, utilizing network addresses of the conflicting computers to resolve which computer of the multiple computers shall be granted exclusive access.

14. A computer-implemented method as in claim 3 further comprising:

defining a full ordering of unique gravities among the corresponding multiple computers to prevent access deadlock, wherein each of the gravities identifies a relative weighting of priority for performing transactions associated with the shared storage.

15. A computer-implemented method as in claim 3 further comprising:

providing transaction manager functionality at the multiple computers in which corresponding transaction managers generate a same unique address in their corresponding unified address spaces for a given file associated with the shared storage.

16. A computer-implemented method as in claim 15 further comprising:

utilizing the same unique address in corresponding unified address space databases at the corresponding transaction managers to identify access property information associated with the given file.

17. A computer-implemented method as in claim 3 further comprising:

supporting communications among the multiple computers on a different communication link than the multiple computers use to access the shared storage.

18. The computer-implemented method as in claim 3 further comprising:

maintaining the corresponding data access information to include a first property object, the first property object being associated with a first range of the unified address space, the first property object specifying computer access rights associated with a first portion of the shared storage corresponding to the first range of the unified address space;

maintaining the corresponding data access information to include a second property object, the second property object being associated with a second range of the unified address space, the second property object specifying computer access rights associated with a second portion of the shared storage corresponding to the second range of unified address space; and

in response to detecting commonality between the first property object and the second property object;

merging the first range and the second range into a single given range of the unified address space;

merging the first property object and the second property object into a single property object; and

associating the single property object with the single given range of the unified address space.

19. The computer-implemented method as in claim 3 further comprising:

maintaining the corresponding data access information to include a first property object, the first property object being associated with a first range of the unified address space, the first property object specifying computer access rights associated with a first portion of the shared storage corresponding to the first range;

in response to receiving a request to apply an operation with respect to the shared storage corresponding to a sub-portion of the first range;

subdividing the first range into a first sub-range of the unified address space and a second sub-range of the unified address space;

cloning the first object into a second property object;

associating the first property object with the first sub-range; and

associating the second property object with the second sub-range.

20. A computer system for managing access to shared storage, the computer system comprising:

a processor;

a memory unit that stores instructions associated with an application executed by the processor;

a communication interface that supports communication with other computers having access to the shared storage; and

an interconnect coupling the processor, the memory unit, and the communication interface, enabling the computer system to execute the application and perform operations of;

providing a transaction manager at each of the multiple computers in the environment to coordinate access to locations in the shared storage, the transaction manager at each of the multiple computers utilizing a unified address space that maps locations in the shared storage to corresponding access properties maintained by respective transaction managers, the access properties indicating an access status of the locations associated with the shared storage, the transaction managers at each of the multiple computers supporting operations of;

receiving a request to access data stored in the shared storage;

identifying a unique address in a unified address space associated with the data stored in the shared storage;

utilizing the unique address to retrieve access properties associated with the data in the shared storage; and

based on the retrieved access properties, identifying whether other computers in the environment have requested contemporaneous access to the data and, if so, communicating with transaction managers at the other computers accessing a common storage location of the shared storage to resolve conflicts associated with multiple computers attempting to access the common storage location of the shared storage;

at each of the multiple computers;

maintaining the unified address space to span a range of address values, each of the address values corresponding to respective storage capacity in the shared storage;

producing boundaries within the unified address space; and

utilizing the boundaries to define ranges in the unified address space, the ranges in the unified address space representing corresponding portions of storage capacity in the shared storage;

maintaining a respective property object for each of the ranges in the unified address space, each respective property object indicating access rights to a respective portion of the shared storage to which a range pertains;

at a first computer of the multiple computers, receiving a request to access a file in the shared storage;

converting an identifier associated with the file to an address value in the unified address space;

based on the address value in the unified address space, identifying a specific range in the unified address space in which the address value resides;

accessing a property object for the specific range in the unified address space; and

analyzing the property object to identify which, if any, of the multiple computers has current access rights to the file.