Hierarchical approach to indentifying changing device characteristics

• US 6,701,392 B1
• Filed: 11/30/2001
• Issued: 03/02/2004
• Est. Priority Date: 11/14/2001
• Status: Expired due to Term

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Halstead, Mark J., Ofer, Adi, Arnon, Dan
• Primary Examiner(s): Gaffin, Jeffrey
• Assistant Examiner(s): CHEN, ALAN S
• Application Number:
  US09/998,494
• Time in Patent Office: 823 Days
• Field of Search: 710/5, 710/16, 710/36, 710/37, 710/38, 711/122
• US Class Current: 710/36
• CPC Class Codes: G06F 11/1666 where the redundant component is memory or memory area
• CPC Class Codes: G06F 11/20 using active fault-masking, e.g. by switching out faulty elements or by switching in spare elements
• CPC Class Codes: G06F 11/2069 Management of state, configuration or failover
• 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

Abstract

Determining device characteristics includes obtaining a first globally accessible value, if the first globally accessible value corresponds to a stored first value, obtaining device characteristics data from a relatively fast memory, if the first globally accessible value does not correspond to the stored first value, obtaining a second globally accessible value, if the second globally accessible value corresponds to a stored second value, obtaining device characteristics data from a relatively fast memory, if the second globally accessible value does not correspond to the stored second value, obtaining device characteristics data from a relatively slow memory and updating the relatively fast memory, the stored first value, and the stored second value. The globally accessible first value may include device I/O information. The globally accessible values may be stored in global memory that is accessible to a plurality of processors.

Claims

1. A method of accessing a device, comprising:

obtaining status information that indicates how to access the device;

examining at least a portion of the status information to determine if configuration of the device has changed;

if the configuration of the device has not changed, accessing stored configuration data from a first memory, wherein the first memory is not accessible to all of a plurality of processors; and

if the configuration of the device has changed, accessing new configuration information from a second memory and updating the stored configuration data with the new configuration information, wherein the second memory is accessible to all of the plurality of processors.

2. A method, according to claim 1, wherein the first memory is local to a processor that accesses the first memory.

3. A method, according to claim 1, wherein the stored configuration data indicates whether a device is a source or a destination for data in a remote data communication link.

4. A method, according to claim 1, wherein examining at least a portion of the status information includes determining whether the portion of the status information is equal to a first stored value.

5. A method, according to claim 4, further comprising:

if the portion of the status information is not equal to the first stored value, obtaining additional status information and determining if a portion of the additional status information is equal to a second stored value.

6. A method, according to claim 5, further comprising:

following updating the stored configuration data, updating the first and second stored values.

7. A computer program product that accesses a device, comprising:

executable code that obtains status information that indicates how to access the device;

executable code that examines at least a portion of the status information to determine if configuration of the device has changed;

executable code that accesses stored configuration data from a first memory if the configuration of the device has not changed, wherein the first memory is not accessible to all of a plurality of processors; and

executable code that accesses new configuration information from a second memory and updates the stored configuration data with the new configuration information if the configuration of the device has changed, wherein the second memory is accessible to all of the plurality of processors.

8. A computer program product, according to claim 7, wherein the stored configuration data indicates whether a device is a source or a destination for data in a remote data communication link.

9. A computer program product, according to claim 7, wherein executable code that examines at least a portion of the status information includes executable code that determines whether the portion of the status information is equal to a first stored value.

10. A computer program product, according to claim 9, further comprising:

executable code that obtains additional status information and determines if a portion of the additional status information is equal to a second stored value if the portion of the status information is not equal to the first stored value.

11. A computer program product, according to claim 10, further comprising:

executable code that updates the first and second stored values following updating the stored configuration data.

12. Apparatus that accesses a device, comprising:

means for obtaining status information that indicates how to access the device;

means for examining at least a portion of the status information to determine if configuration of the device has changed;

means for accessing stored configuration data from a first memory if the configuration of the device has not changed, wherein the first memory is not accessible to all of a plurality of processors; and

means for accessing new configuration information from a second memory and updating the stored configuration data with the new configuration information if the configuration of the device has changed, wherein the second memory is accessible to all of the plurality of processors.

13. Apparatus, according to claim 12, wherein the first memory is local to a processor that accesses the first memory.

14. Apparatus, according to claim 12, wherein the stored configuration data indicates whether a device is a source or a destination for data in a remote data communication link.

15. Apparatus, according to claim 12, wherein means for examining at least a portion of the status information includes means for determining whether the portion of the status information is equal to a first stored value.

16. Apparatus, according to claim 15, further comprising:

means for obtaining additional status information and determining if a portion of the additional status information is equal to a second stored value if the portion of the status information is not equal to the first stored value.

17. Apparatus, according to claim 16, further comprising:

means for updating the first and second stored values following updating the stored configuration data.