System and method for hijacking inodes based on replication operations received in an arbitrary order

• US 9,858,001 B2
• Filed: 01/22/2016
• Issued: 01/02/2018
• Est. Priority Date: 09/14/2009
• Status: Active Grant

• Current Assignee: NetApp, Inc.
• Original Assignee: NetApp, Inc.
• Inventors: Shah, Devang K., Driscoll, Alan S.
• Primary Examiner(s): Bullock, Joshua
• Application Number:
  US15/004,470
• Publication Number:
  US 20160139843A1
• Time in Patent Office: 711 Days
• Field of Search: 707610
• CPC Class Codes: G06F 16/178 Techniques for file synchronisation in file systems
• CPC Class Codes: G06F 16/2365 Ensuring data consistency and integrity
• CPC Class Codes: G06F 16/27 Replication, distribution or synchronisation of data between databases or within a distributed database system; Distributed database system architectures therefor
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/065 Replication mechanisms
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]

Abstract

A system and method for hijacking inodes based on replication operations received in an arbitrary order is used to assist a data replication operation from a source storage system to a destination storage system. The source storage system generates a set of replication operations as part of a replication process and transmits the replication operations in an arbitrary order. After receiving a replication operation, the system determines whether the operation is inconsistent with a corresponding destination inode. If an inconsistency exists, the system hijacks the destination inode by replacing the destination inode'"'"'s metadata with data determined based on the replication operation. The system may also delete metadata from the inode and/or initialize metadata to default values if the metadata was not replaced based on the replication operation. The system then waits for a second replication operation that contains the remaining metadata and replaces the metadata based on the second replication operation. In addition, data blocks associated with the previous version of the inode are freed.

Claims

1. A computing device, comprising:

a memory containing computer-readable storage medium having stored thereon instructions for performing a method; and

a processor coupled with the memory, the processor configured to execute the instructions to cause the processor to;

receive, by a first storage system from a second storage system, a first replication operation that is to modify a first inode at the first storage system, wherein the first replication operation specifies that the first inode is expected to have a first inode type;

determine that the first inode has a second inode type;

determine that the first replication operation has been received by the first storage system out of order relative to an order for which a corresponding operation was executed at the second storage system based upon the first inode type not matching the second inode type;

populate a first portion of inode metadata of the first inode based upon the first replication operation;

initialize a remaining portion of the inode metadata to default values;

receive a second replication operation that is to modify the first inode; and

populate the remaining portion of the inode metadata based upon the second replication operation.

2. The computing device of claim 1, wherein the first replication operation comprises a modify operation and the second replication operation comprises a create operation, wherein the create operation was performed before the modify operation for a source metadata container, and wherein the modify operation is performed before the create operation for a destination metadata container associated with the first inode.

3. The computing device of claim 1, wherein the instructions cause the processor to:

determine that a target generation identifier targeted by the first replication operation differs from a current generation identifier of a destination metadata container associated with the first inode.

4. The computing device of claim 1, wherein the instructions cause the processor to:

determine that the first replication operation is directed to modify a destination metadata container associated with the first inode that has an unused status.

5. The computing device of claim 1, wherein the instructions cause the processor to:

determine that the second replication operation is directed to create a destination metadata container associated with the first inode that already exists.

6. The computing device of claim 1, wherein the instructions cause the processor to:

detect an inconsistency between the first replication operation and a destination metadata container associated with the first inode based upon the first replication operation including a modify operation that is directed to a metadata container type that differs from a destination metadata container type of the destination metadata container.

7. The computing device of claim 1, wherein the instructions cause the processor to:

determine that the first replication operation is inconsistent with a metadata container type of a destination metadata container associated with the first inode.

8. A method, comprising:

receiving, by a first storage system from a second storage system, a first replication operation that is to modify a first inode at the first storage system, wherein the first replication operation specifies that the first inode is expected to have a first inode type;

determining that the first inode has a second inode type;

determining that the first replication operation has been received by the first storage system out of order relative to an order for which a corresponding operation was executed at the second storage system based upon the first inode type not matching the second inode type;

populating a first portion of inode metadata of the first inode based upon the first replication operation;

initializing a remaining portion of the inode metadata to default values;

receiving a second replication operation that is to modify the first inode; and

populating the remaining portion of the inode metadata based upon the second replication operation.

9. The method of claim 8, comprising:

determining that a target generation identifier targeted by the first replication operation differs from a current generation identifier of a destination metadata container associated with the first inode.

10. The method of claim 8, comprising:

detecting an inconsistency between the first replication operation and a destination metadata container associated with the first inode based upon the first replication operation including a modify operation that is directed to a metadata container type that differs from a destination metadata container type of the destination metadata container; and

replacing content of the first part of the destination metadata container with the first metadata in response to the inconsistency.

11. The method of claim 10, wherein detecting the inconsistency comprises:

determining that the first replication operation is directed to modify the destination metadata container that has an unused status.

12. The method of claim 8, wherein the first replication operation is to add data blocks to a destination metadata container of a directory.

13. The method of claim 10, wherein the destination metadata container is a file and wherein the replacing comprises:

freeing a first set of metadata blocks associated with the file; and

associating a second set of metadata blocks, associated with the first the replication operation, with the file.

14. The method of claim 8, wherein the first replication operation is to add a directory entry to a destination metadata container of a file.

15. A non-transitory computer readable medium comprising instructions that, when executed by a processor, cause the processor to:

receive, by a first storage system from a second storage system, a first replication operation that is to modify a first inode at the first storage system, wherein the first replication operation specifies that the first inode is expected to have a first inode type;

determine that the first inode has a second inode type;

determine that the first replication operation has been received by the first storage system out of order relative to an order for which a corresponding operation was executed at the second storage system based upon the first inode type not matching the second inode type;

populate a first portion of inode metadata of the first inode based upon the first replication operation;

initialize a remaining portion of the inode metadata to default values;

receive a second replication operation that is to modify the first inode; and

populate the remaining portion of the inode metadata based upon the second replication operation.

16. The non-transitory computer readable medium of claim 15, wherein the first replication operation includes a target metadata container identifier.

17. The non-transitory computer readable medium of claim 15, wherein the instructions cause the processor to:

detect an inconsistency between the first replication operation and a destination metadata container associated with the first inode based upon the first replication operation including a modify operation that is directed to a metadata container type that differs from a destination metadata container type of the destination metadata container; and

replace content of the first part of the destination metadata container with the first metadata in response to the inconsistency.

18. The non-transitory computer readable medium of claim 17, wherein the destination metadata container is a file and wherein the replacing comprises:

freeing a first set of metadata blocks associated with the file; and

associating a second set of metadata blocks, associated with the first the replication operation, with the file.

19. The non-transitory computer readable medium of claim 15, wherein the instructions cause the processor to:

detect an inconsistency based upon a determination that the second replication operation is directed to create a destination metadata container that already exists.

20. The non-transitory computer readable medium of claim 15, wherein the instructions cause the processor to:

determine that the first replication operation is directed to modify a destination metadata container that has an unused status.