Dynamic and variable length extents

• US 20030140210A1
• Filed: 08/13/2002
• Published: 07/24/2003
• Est. Priority Date: 12/10/2001
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: Incipient Inc.
• Inventors: Testardi, Richard
• Granted Patent: US 6,959,373 B2
• Time in Patent Office: Days
• US Class Current: 711/203
• CPC Class Codes: G06F 12/0292 using tables or multilevel address translation means G06F12/023 takes precedence; address translation in virtual memory systems G06F12/10
• CPC Class Codes: G06F 2003/0697 device management, e.g. handlers, drivers, I/O schedulers
• CPC Class Codes: G06F 3/0601 Interfaces specially adapted for storage systems
• CPC Class Codes: G06F 3/0613 in relation to throughput
• CPC Class Codes: G06F 3/0635 by changing the path, e.g. traffic rerouting, path reconfiguration
• CPC Class Codes: G06F 3/0647 Migration mechanisms
• CPC Class Codes: G06F 3/065 Replication mechanisms
• CPC Class Codes: G06F 3/0664 at device level, e.g. emulation of a storage device or system
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD

Abstract

Described are techniques used in a computer system for handling data operations to storage devices. A switching fabric includes one or more fast paths for handling lightweight, common data operations and at least one control path for handling other data operations. A control path manages one or more fast paths. The fast path and the control path are utilized in mapping virtual to physical addresses using mapping tables. The mapping tables include an extent table of one or more entries corresponding to varying address ranges. The size of an extent may be changed dynamically in accordance with a corresponding state change of physical storage. The fast path may cache only portions of the extent table as needed in accordance with a caching technique. The fast path may cache a subset of the extent table stored within the control path. A set of primitives may be used in performing data operations. A locking mechanism is described for controlling access to data shared by the control paths.

Claims

1. A method executed in a computer system for performing virtual to physical address mapping of a virtual address comprising:

determining a volume descriptor associated with said virtual address, said volume descriptor including a variable size extent table, said variable size extent table including a plurality of portions, each of said portions associated with a varying range of virtual addresses;

determining a first extent included in said variable size extent table corresponding to said virtual address; and

determining a corresponding physical address for said virtual address using mapping table information associated with said first extent.

2. The method of claim 1, wherein said variable size extent table includes a first extent and a second extent, said first extent corresponding to a first range of virtual addresses, said second extent corresponding to a second range of virtual addresses, said first and second ranges of virtual address being of different sizes.

3. The method of claim 2, further comprising:

dynamically modifying said first range of virtual addresses associated with said first extent in response to a state change of physical data storage corresponding to said first range of virtual addresses.

4. The method of claim 2, further comprising:

creating a second extent corresponding to a state change of physical storage associated with said second extent.

5. The method of claim 4, wherein a portion of said mapping table information is included in a storage redirect table having at least one entry.

6. The method of claim 5, wherein each entry in said storage redirect table includes physical storage address information and state information corresponding to a physical storage location.

7. The method of claim 6, wherein said variable size extent table includes, for each extent, an index into the storage redirect table corresponding to an entry in the storage redirect table.

8. The method of claim 7, wherein at least two extents included in said variable size extent table are associated with the same index into the storage redirect table.

9. A computer program product that performs virtual to physical address mapping of a virtual address comprising:

machine executable code that determines a volume descriptor associated with said virtual address, said volume descriptor including a variable size extent table, said variable size extent table including a plurality of portions, each of said portions associated with a varying range of virtual addresses;

machine executable code that determines a first extent included in said variable size extent table corresponding to said virtual address; and

machine executable code that determines a corresponding physical address for said virtual address using mapping table information associated with said first extent.

10. The computer program product of claim 9, wherein said variable size extent table includes a first extent and a second extent, said first extent corresponding to a first range of virtual addresses, said second extent corresponding to a second range of virtual addresses, said first and second ranges of virtual address being of different sizes.

11. The computer program product of claim 10, further comprising:

machine executable code that dynamically modifies said first range of virtual addresses associated with said first extent in response to a state change of physical data storage corresponding to said first range of virtual addresses.

12. The computer program product of claim 10, further comprising:

machine executable code that creates a second extent corresponding to a state change of physical storage associated with said second extent.

13. The computer program product of claim 12, wherein a portion of said mapping table information is included in a storage redirect table having at least one entry.

14. The computer program product of claim 13, wherein each entry in said storage redirect table includes physical storage address information and state information corresponding to a physical storage location.

15. The computer program product of claim 14, wherein said variable size extent table includes, for each extent, an index into the storage redirect table corresponding to an entry in the storage redirect table.

16. The computer program product of claim 15, wherein at least two extents included in said variable size extent table are associated with the same index into the storage redirect table.