Reducing Latency of Access Requests in Distributed Storage Systems Having a Shared Data Set

• US 20110145189A1
• Filed: 02/24/2011
• Published: 06/16/2011
• Est. Priority Date: 01/15/2008
• Status: Active Grant

• Current Assignee: NetApp, Inc.
• Original Assignee: NetApp, Inc.
• Inventors: Palekar, Amber, Zheng, Cindy, Khona, Rahul
• Granted Patent: US 8,171,100 B2
• Time in Patent Office: Days
• US Class Current: 707/620
• CPC Class Codes: G06F 16/176 Support for shared access to files; File sharing support
• CPC Class Codes: H04L 67/1097 for distributed storage of data in networks, e.g. transport arrangements for network file system [NFS], storage area networks [SAN] or network attached storage [NAS]

Abstract

Described are methods and apparatus for reducing latency of read and write requests for a set of storage system sites having a shared data set. An owner site may directly write to the shared data set and contains current data regarding the shared data set. The remote sites may experience substantial latency when accessing the shared data set stored at the owner site. Synchronizing and caching methods may reduce overall read latency experienced at remote sites by periodically transmitting images of the shared data set to the remote sites. Also, a migration method may be used to change ownership of the shared data set from a current owner site (that may be receiving a relatively low number of read/write requests) to a new owner site (that may be receiving a relatively high number of read/write requests) to reduce the overall read and write latency experienced in the sites.

Claims

1. A system for caching data in a plurality of storage systems, each storage system accessing a same shared data set comprising a set of storage objects, each storage object having an associated set of attributes that describe the storage object, the system comprising:

the owner storage system configured for storing the shared data set, the owner storage system comprising;

an owner synchronizing module configured for;

generating and transmitting a first image of the shared data set to a remote storage system over a network; and

an owner caching module configured for;

receiving an attribute request from the remote storage system for owner attributes of a first storage object in the shared data set; and

transmitting the owner attributes of the first storage object to the remote storage system over the network; and

the remote storage system comprising;

a remote synchronizing module configured for;

receiving and storing the first image of the shared data set to the remote storage system; and

a remote caching module configured for;

receiving a read request for a first data of the first storage object; and

sending an attribute request to the owner storage system for owner attributes of the first storage object; and

a network connecting the owner storage system and the remote storage system.

2. The system of claim 1, wherein the remote caching module is further configured for:

receiving the owner attributes of the first storage object from the owner storage system;

retrieving remote attributes of the first storage object from the first image;

determining that the owner and remote attributes of the first storage object match; and

retrieving the first data of the first storage object from the first image.

3. The system of claim 2, wherein the remote caching module is further configured for:

storing first information indicating that the owner and remote attributes of the first storage object match;

receiving a read request for a second data of the first storage object;

using the first information to determine that the owner and remote attributes of the first storage object match; and

retrieving the second data of the first storage object from the first image.

4. The system of claim 1, wherein the remote caching module is further configured for:

receiving the owner attributes of the first storage object from the owner storage system;

retrieving remote attributes of the first storage object from the first image;

determining that the owner and remote attributes of the first storage object do not match; and

sending a read request to the owner storage system for the first data from the first storage object.

5. The system of claim 4, wherein the remote caching module is further configured for:

storing first information indicating that the owner and remote attributes of the first storage object do not match;

receiving a read request for a second data of the first storage object;

using the first information to determine that the owner and remote attributes of the first storage object do not match; and

sending a read request to the owner storage system for the second data from the first storage object.

6. The system of claim 1, wherein the owner caching module is further configured for:

generating and transmitting subsequent images of the shared data set to the remote storage system over the network, wherein a subsequent image may comprise changes to the shared data set since a previous image was generated, wherein the generating and transmitting are performed at predetermined time intervals automatically without human initiation or intervention.

7. The system of claim 1, wherein:

the set of attributes that describe a storage object comprise information indicating when the storage object was last modified; and

an attribute request for a storage object comprises a read request specifying no block range or a zero block range of a storage object which causes a return of the attributes of the storage object and no data of the storage object.

8. A method for caching data in a plurality of storage systems, each storage system accessing a same shared data set comprising a set of storage objects, each storage object having an associated set of attributes that describe the storage object, the method comprising:

storing the shared data set at an owner storage system;

generating and transmitting a first image of the shared data set to a remote storage system over a network;

receiving and storing the first image of the shared data set to the remote storage system;

receiving, at the remote storage system, a read request for a first data of the first storage object;

sending an attribute request to the owner storage system for owner attributes of the first storage object;

retrieving owner attributes of the first storage object in the shared data set stored to the owner storage system; and

transmitting the owner attributes of the first storage object to the remote storage system over the network.

9. The method of claim 8, further comprising:

receiving the owner attributes of the first storage object from the owner storage system;

retrieving remote attributes of the first storage object from the first image;

determining that the owner and remote attributes of the first storage object match; and

retrieving the first data of the first storage object from the first image.

10. The method of claim 9, further comprising:

storing first information indicating that the owner and remote attributes of the first storage object match;

receiving, at the remote storage system, a read request for a second data of the first storage object;

using the first information to determine that the owner and remote attributes of the first storage object match; and

retrieving the second data of the first storage object from the first image.

11. The method of claim 8, further comprising:

retrieving remote attributes of the first storage object from the first image;

determining that the owner and remote attributes of the first storage object do not match; and

sending a read request to the owner storage system for the first data from the first storage object.

12. The method of claim 11, further comprising:

storing first information indicating that the owner and remote attributes of the first storage object do not match;

receiving, at the remote storage system, a read request for a second data of the first storage object;

using the first information to determine that the owner and remote attributes of the first storage object do not match; and

sending a read request to the owner storage system for the second data from the first storage object.

13. The method of claim 8, further comprising:

generating and transmitting subsequent images of the shared data set to the remote storage system over the network, wherein a subsequent image may comprise changes to the shared data set since a previous image was generated, wherein the generating and transmitting are performed at predetermined time intervals automatically without human initiation or intervention.

14. The method of claim 8, wherein:

the set of attributes that describe a storage object comprise information indicating when the storage object was last modified; and

an attribute request for a storage object comprises a read request specifying no block range or a zero block range of a storage object which causes a return of the attributes of the storage object and no data of the storage object.

15. A non-transitory computer readable medium having instructions stored thereon when executed by a processor, caches data in a plurality of storage systems, each storage system accessing a same shared data set comprising a set of storage objects, each storage object having an associated set of attributes that describe the storage object, the non-transitory computer readable medium comprising sets of instructions for:

storing the shared data set at an owner storage system;

generating and transmitting a first image of the shared data set to a remote storage system over a network;

receiving and storing the first image of the shared data set to the remote storage system;

receiving, at the remote storage system, a read request for a first data of the first storage object;

sending an attribute request to the owner storage system for owner attributes of the first storage object;

retrieving owner attributes of the first storage object in the shared data set stored to the owner storage system; and

transmitting the owner attributes of the first storage object to the remote storage system over the network.

16. The non-transitory computer readable medium of claim 15, further comprising sets of instructions for:

receiving the owner attributes of the first storage object from the owner storage system;

retrieving remote attributes of the first storage object from the first image;

determining that the owner and remote attributes of the first storage object match; and

retrieving the first data of the first storage object from the first image.

17. The non-transitory computer readable medium of claim 16, further comprising sets of instructions for:

storing first information indicating that the owner and remote attributes of the first storage object match;

receiving, at the remote storage system, a read request for a second data of the first storage object;

using the first information to determine that the owner and remote attributes of the first storage object match; and

retrieving the second data of the first storage object from the first image.

18. The non-transitory computer readable medium of claim 15, further comprising sets of instructions for:

retrieving remote attributes of the first storage object from the first image;

determining that the owner and remote attributes of the first storage object do not match; and

sending a read request to the owner storage system for the first data from the first storage object.

19. The non-transitory computer readable medium of claim 18, further comprising sets of instructions for:

storing first information indicating that the owner and remote attributes of the first storage object do not match;

receiving, at the remote storage system, a read request for a second data of the first storage object;

using the first information to determine that the owner and remote attributes of the first storage object do not match; and

sending a read request to the owner storage system for the second data from the first storage object.

20. The non-transitory computer readable medium of claim 15, further comprising sets of instructions for:

generating and transmitting subsequent images of the shared data set to the remote storage system over the network, wherein a subsequent image may comprise changes to the shared data set since a previous image was generated, wherein the generating and transmitting are performed at predetermined time intervals automatically without human initiation or intervention.

21. The non-transitory computer readable medium of claim 15, wherein:

the set of attributes that describe a storage object comprise information indicating when the storage object was last modified; and

an attribute request for a storage object comprises a read request specifying no block range or a zero block range of a storage object which causes a return of the attributes of the storage object and no data of the storage object.