Extended storage capacity for a network file server

• US 20040267832A1
• Filed: 04/26/2004
• Published: 12/30/2004
• Est. Priority Date: 04/24/2003
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: NeoPath Networks, Inc. (Cisco Systems, Inc.)
• Inventors: Wong, Thomas K., Chawla, Rajeev, Tsirigotis, Panagiotis, Iyengar, Anand
• Granted Patent: US 7,072,917 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 16/10 File systems; File servers
• CPC Class Codes: H04L 67/1095 Replication or mirroring of data, e.g. scheduling or transport for data synchronisation between network nodes
• 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]
• CPC Class Codes: H04L 69/329 in the application layer [OSI layer 7]
• CPC Class Codes: Y10S 707/955 Object-oriented
• CPC Class Codes: Y10S 707/99942 Manipulating data structure, e.g. compression, compaction, compilation
• CPC Class Codes: Y10S 707/99953 Recoverability
• CPC Class Codes: Y10S 707/99956 File allocation

Abstract

A NAS switch provides extended storage capacity to a file server in a decentralized storage network such as a NAS (Network Attached Storage) storage network. The NAS switch sits in the data path of a client on the front end and a directory file server and shadow file servers on the back end. A segregation module in the NAS switch replicates data from the directory file server to a shadow file server, and then replaces the data in the directory file server with holey files. Holey files, which store a range of consecutive values such as zero with negligible storage space, retain the attributes of the data without retaining its storage consumption. Thus, the directory file server can server as a single directory hierarchy for several shadow file servers containing data beyond a capacity of the directory file server. When the NAS switch receives operations from the client, an association module forwards directory operations to the directory file server and data operations to the shadow file server. The NAS switch also provides services to several shadow file servers from a single directory file server.

Claims

1. A method for extending the storage capacity of a file server in a decentralized storage network, comprising:

storing data for an object on a shadow file server;

storing metadata for the object on a directory file server having a capacity such that the directory file server is capable of appearing to store more data than the capacity;

adding an entry to a directory server table to associate the data and the metadata for reconstruction of the object.

2. The method of claim 1, wherein the storing metadata comprises storing a holey file, comprising a range of consecutive data values based on a first size of the object, to have the appearance of storing the object data.

3. The method of claim 2, further comprising:

modifying the shadow file to a second size; and

changing the offset of data values based on the second size.

4. The method of claim 1, further comprising:

receiving the object from a client for storage on the storage network.

5. The method of claim 1, further comprising:

converting an existing file server to the directory file server by moving data to the shadow file server and replacing files with holey files having the appearance of storing data.

6. The method of claim 1, further comprising:

naming a shadow file containing the data with a hash function.

7. The method of claim 1, wherein the directory server table associates one or more directories of the directory file server with a shadow file server.

8. The method of claim 1, further comprising:

adding an entry to a file location cache to associate a switch file handle used by a client to access the object from the NAS switch with a shadow file handle used by the NAS switch to access the shadow file from the shadow file server.

9. The method of claim 8, further comprising:

receiving a request to access the object with the switch file handle;

looking-up the shadow file handle in the file location cache; and

submitting the access request using the shadow file handle.

10. The method of claim 9, further comprising:

removing entries from the file location cache responsive to surpassing a capacity;

responsive to not finding the shadow NAS file handle in the file location cache, looking-up a directory associated with the object in the directory server table to obtain the associated shadow file server; and

submitting the request to the shadow file server.

11. The method of claim 1, further comprising:

receiving a request to access the object that affects the directory; and

submitting the request to the directory file server.

12. The method of claim 11, wherein the request comprises one from the group consisting of:

create directory, delete directory, and move directory.

13. The method of claim 1, further comprising:

receiving a request to access object that affects the shadow file; and

submitting the request to the shadow file server.

14. The method of claim 13, wherein the request comprises one from the group consisting of:

create file, delete file, move file, copy file, read file, and write file.

15. The method of claim 1, further comprising:

receiving a request to access object that affects the directory and the shadow file; and

submitting the request to the directory file server and the shadow file server.

16. The method of claim 15, wherein the request comprises one from the group consisting of:

create file, delete file, move file, copy file, and truncate file.

17. The method of claim 1, further comprising:

providing a file service to the shadow file located on the shadow file server from the directory file server.

18. The method of claim 17, wherein the file service comprises file locking to preserve data integrity of the shadow file during multiple accesses.

19. The method of claim 1, wherein the object comprises a directory hierarchy having objects representatives of sub-directories and files.

20. The method of claim 1, wherein the object comprises a file.

21. The method of claim 1, further comprising:

mapping a switch file handle that is independent of a location of the object to a first NAS file handle that is indicative of a first location of the metadata.

22. The method of claim 21, further comprising:

storing the data at a second location; and

mapping the switch handle to a second NAS file handle that is indicative of the second location.

23. A NAS (Network Attached Storage) switch to extend the storage capacity of a file server in a NAS storage network, comprising:

a segregation module to segregate an object by storing data for an object on a shadow file server, and metadata for the object on a directory file server having a capacity such that the directory file server is capable of appearing to store more data than the capacity, the segregation module associating the data and metadata in a directory server table;

an association module to retrieve the object from the data and the metadata in the directory server table.

24. The NAS switch of claim 23, wherein the segregation module stores a holey file in the directory file server, comprising a range of consecutive data values based on a first size of the object, to have the appearance of storing the object data.

25. The NAS switch of claim 24, wherein the segregation module modifies the shadow file to a second size and changes the offset of data values based on the second size.

26. The NAS switch of claim 23, further comprising:

a client module to receive the object from a client for storage on the storage network.

27. The NAS switch of claim 23, wherein the segregation module converts an existing file server to the directory file server by moving data to the shadow file server and replacing files with holey files having the appearance of storing data.

28. The NAS switch of claim 23, further comprising:

a file naming module to name a shadow file containing the data with a hash function.

29. The NAS switch of claim 23, wherein the directory server table associates one or more directories of the directory file server with a shadow file server.

30. The NAS switch of claim 23, further comprising:

a file location cache,

wherein the segragation module adds an entry to the file location cache, the entry comprising a switch file handle used by a client to access the object from the NAS switch in association with a shadow NAS file handle from the shadow file server.

31. The NAS switch of claim 30, further comprising:

a client module to receive a request to access the object with a switch file handle; and

a file server interface to submit the request to the shadow file server,

wherein the association module looks-up the shadow file handle in the file location cache.

32. The NAS switch of claim 31, wherein the file location cache removes entries responsive to surpassing a capacity, and the association module looks-up the object in the directory server table to obtain the associated shadow file server responsive to not finding the shadow file handle in the file location cache, and the file server interface submits the request to the shadow file server.

33. The NAS switch of claim 23, wherein the segregation module receives a request to access the object that affects the directory, and a file server interface submits the request to the directory file server.

34. The NAS switch of claim 33, wherein the request comprises one from the group consisting of:

create directory, delete directory, and move directory.

35. The NAS switch of claim 23, wherein the segregation module, responsive to receiving a request to access object that affects the shadow file, submits the request to the shadow file server.

36. The NAS switch of claim 35, wherein the request comprises one from the group consisting of:

create file, delete file, move file, copy file, read file, and write file.

37. The NAS switch of claim 23, wherein the segregation module, responsive to receiving a request to access object that affects the directory, submits the request to the directory file server and the shadow file server.

38. The NAS switch of claim 37, wherein the request comprises one from the group consisting of:

create file, delete file, move file, copy file, and truncate file.

39. The NAS switch of claim 23, wherein the directory service provides a file service to the shadow file located on the shadow file server.

40. The NAS switch of claim 39, wherein the file service comprises file locking to preserve data integrity of the shadow file during multiple accesses.

41. The NAS switch of claim 23, wherein the object comprises a directory hierarchy having objects representatives of sub-directories and files.

42. The NAS switch of claim 23, wherein the object comprises a file.

43. A computer program product, comprising a computer-readable medium having computer program instructions for a method of extending the storage capacity of a file server in a decentralized storage network, the method comprising the steps of:

storing data for an object on a shadow file server;

storing metadata for the object on a directory file server having a capacity such that the directory file server is capable of appearing to store more data than the capacity;

adding an entry to a directory server table to associate the data and the metadata for reconstruction of the object.

44. The computer program product of claim 43, wherein the storing metadata comprises storing a holey file, comprising a range of consecutive data values based on a first size of the object, to have the appearance of storing the object data.

45. A NAS (Network Attached Storage) switch to access an object in a storage network, comprising:

a means for segregating data of an object, for storage on a shadow file server, from metadata of the object, for storage on a directory file server having a storage capacity, such that the directory file server is capable of appearing to store more data than the storage capacity; and

a means for associating the data and the metadata in a directory server table.