Methods and apparatus for interfacing to a data storage system

• US 7,620,790 B1
• Filed: 10/04/2007
• Issued: 11/17/2009
• Est. Priority Date: 06/29/1999
• Status: Expired due to Fees

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Blumenau, Steven M.
• Primary Examiner(s): Thai; Tuan V.
• Application Number:
  US11/867,330
• Time in Patent Office: 775 Days
• Field of Search: 711/100, 711/111, 711/112, 711/154, 711/170
• US Class Current: 711/170
• CPC Class Codes: G06F 3/0607 by facilitating the process of upgrading existing storage systems, e.g. for improving compatibility between host and storage device
• CPC Class Codes: G06F 3/0608 Saving storage space on storage systems
• CPC Class Codes: G06F 3/0631 by allocating resources to storage systems
• CPC Class Codes: G06F 3/0665 at area level, e.g. provisioning of virtual or logical volumes
• CPC Class Codes: G06F 3/0685 Hybrid storage combining heterogeneous device types, e.g. hierarchical storage, hybrid arrays

Abstract

A data storage system includes methods and apparatus that provide volumes for access by host computing devices. The volumes can have a storage size that is independently configurable from an actual amount of data storage that may or may not be associated with the volume. The volumes also have a persistent identifier. The volumes can have any amount of associated storage space allocated to the volume, including none, within the data storage system. Since the storage size and associated storage space are each independently configurable from each other, host that interface with the data storage system can perceive the volumes as being larger than they really are. A dynamic volume configuration technique is provided which allows storage space within storage devices in the data storage system to be dynamically associated and disassociated (i.e., added and removed) from the volumes on an as-needed basis, without requiring disruption of host activities with respect to the volumes. The persistent identifier of a volume allows all hosts and other data storage systems to “see” the volume. This allows a volume in one data storage system to have associated storage space from another volume in another data storage system. Using these techniques, the invention allows software applications and operating systems on hosts that interface to the data storage system to perceive that a volume is always present on the data storage system, even if storage space understood to be associated with the volume from the host'"'"'s perspective is allocated elsewhere or is non-existent.

Claims

1. A computer-implemented method in which a computer system initiates execution of software instructions retrieved from memory, the computer-implemented method comprising:

creating a volume for storing data associated with a storage area network, the volume having multiple reference values;

utilizing the multiple reference values to specify locations of actual storage space associated with the volume, the actual storage space associated with the volume being allocated for use by the volume to store data;

setting a given reference of the multiple references to a null value, the null value indicating that no actual storage space is associated with the given reference for storing data in the volume; and

providing access to the volume.

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

adding an amount of actual storage space associated with the volume via modification of the given reference.

3. The computer-implemented method as in claim 2, wherein adding the amount of actual storage space occurs in response to receiving a request to access the volume.

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

assigning a size value to the volume, the size value indicating an incorrect amount of actual storage space associated with the volume for storing of the data; and

utilizing the size value to provide an indication of a corresponding size of the volume to at least one computer that accesses the volume.

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

receiving a request to access the actual storage space associated with the volume;

identifying an address associated with the request;

based on at least one of the multiple references, determining a specific storage device of the volume corresponding to the address associated with the request; and

retrieving data from the specific storage device based on the address.

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

receiving an identity of a selected storage device in the storage area network, the selected storage device to be associated with the volume for increasing an amount of the actual storage space associated with the volume for storing the data; and

associating the selected storage device with the volume by modifying at least one of the multiple references to point to the selected storage device.

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

in response to detecting a need to add actual storage space to the volume, reconfiguring at least one of the multiple references by replacing a null value with a pointer to a particular actual storage device being added to the volume.

8. The computer-implemented method as in claim 1, wherein utilizing the multiple reference values to define the actual storage space includes utilizing a set of pointers to refer to storage devices in the storage area network that are associated with the volume for storing the data.

9. The computer-implemented method as in claim 8 further comprising:

modifying at least one of the multiple reference values to change an amount of actual storage space allocated for use by the volume to store the data.

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

enabling at least one computer to mount and access the volume; and

in response to detecting a write of data to the volume, reconfiguring the volume to include more actual storage space.

11. The computer-implemented method as in claim 10 further comprising:

reconfiguring the volume to include the more actual storage space while the at least one computer is mounted to the volume.

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

enabling at least one computer to access the volume; and

providing an indication to the at least one computer that the volume is capable of storing a specific amount of data, a total amount of actual storage space in the volume for storing data as specified by the multiple references being less than the specific amount.

13. A computer system supporting access to a storage system, the computer system comprising:

a processor;

a memory unit configured to store instructions associated with an application executed by the processor, the processor configured to execute the instructions and support operations of;

maintaining a volume for storing data associated with a storage area network;

utilizing multiple reference values to define actual storage space in the storage area network that is assigned for use by the volume to store the data;

setting a given reference of the multiple references to a null value to indicate that the given reference associated with the volume does not reference any actual storage space in the storage area network; and

enabling access to the volume.

14. A computer system as in claim 13 further supporting operations of:

adding actual storage space to the volume on an as-needed basis via modifications to at least one of the multiple references.

15. A computer system as in claim 13 further supporting operations of:

in response to receiving a request to access the volume, initiating a change to an amount of the actual storage space in the storage area network allocated for use by the volume to store the data.

16. A computer system as in claim 13 further supporting operations of:

assigning a size associated with the volume that is different than an amount of the actual storage space allocated for use by the volume to store the data; and

providing an indication of the size of the volume to at least one computer that access the data stored in the volume.

17. A computer system as in claim 13 further supporting operations of:

enabling at least one computer to mount and access the volume;

in response to detecting an access to the volume, reconfiguring the volume to include more actual storage space; and

reconfiguring the volume to include the more actual storage space while the at least one computer is mounted to the volume.

18. A computer system as in claim 17 further supporting operations of:

in response to detecting a need to add actual storage space to the volume, reconfiguring at least one of the multiple references by replacing a null value with a pointer to a storage device being added to the volume.

19. A computer system as in claim 13 further supporting operations of:

assigning a size value to the volume, the size value indicating an incorrect amount of actual storage space that is actually associated with the volume for storing of the data; and

utilizing the size value to provide an indication of a corresponding size of the volume to at least one computer that accesses the volume.

20. A computer-readable storage medium having instructions stored thereon for processing data information, such that the instructions, when retrieved from the storage and carried out by a processing device, enable the processing device to perform the steps of:

maintaining a volume for storing data associated with a storage area network;

utilizing multiple reference values to define actual storage space in the storage area network that is assigned for use by the volume to store the data;

setting a given reference of the multiple references to a null value to indicate that the given reference associated with the volume does not reference actual storage space in the storage area network; and

enabling access to the volume.