Method, system, and computer readable medium for maintaining the order of write-commands issued to a data storage

• US 7,647,449 B1
• Filed: 09/28/2006
• Issued: 01/12/2010
• Est. Priority Date: 09/28/2006
• Status: Active Grant

• Current Assignee: Veritas Technologies, LLC (Whitehouse Group Ltd.)
• Original Assignee: Symantec Operating Corporation (NortonLifeLock Inc.)
• Inventors: Roy, Subhojit, Pendharkar, Niranjan Sanjiv
• Primary Examiner(s): Peugh; Brian R
• Application Number:
  US11/540,822
• Time in Patent Office: 1,202 Days
• Field of Search: None
• US Class Current: 711/112
• CPC Class Codes: G06F 11/2064 while ensuring consistency
• CPC Class Codes: G06F 11/2074 Asynchronous techniques

Abstract

A method, system, and computer readable medium for maintaining the order of write-commands issued to a data storage, where the write-commands are issued by one or more host. In one embodiment of the present invention the method includes assigning an order-descriptor to each write-command, storing the write-command, storing the order-descriptor, and collating a plurality of order-descriptors and their corresponding write-commands to obtain an ordered write-command stream.

Claims

1. A method for maintaining the order of write-commands issued to a data storage, wherein the write-commands are issued by at least one host, the method comprising:

assigning an order-descriptor to each write-command;

storing the write-command;

storing the order-descriptor; and

collating a plurality of order-descriptors and their corresponding write-commands to obtain an ordered write-command stream;

wherein assigning the order-descriptor to the write-command comprises;

assigning an indicia of order to the write-command; and

constructing the order-descriptor using the indicia of order and metadata information for the write-command.

2. The method of claim 1, wherein constructing the order-descriptor comprises:

receiving the write-command from the host; and

extracting the metadata information from the write-command; and

placing at least some of the metadata information into the order-descriptor.

3. The method of claim 1, wherein constructing the order-descriptor comprises:

receiving the metadata information from the host.

4. The method of claim 1 further comprising sending an acknowledgement message to the host.

5. The method of claim 1 further comprising updating a backup of the data storage using the ordered write-command stream.

6. The method of claim 1 further comprising rolling back the state of the data storage using the ordered write-command stream.

7. The method of claim 1, wherein the indicia of order comprises a time-stamp.

8. The method of claim 1, wherein the indicia of order comprises a monotonically increasing number.

9. The method of claim 1, wherein the metadata information comprises at least one of:

an initiator of the write-command;

a target volume of the write-command;

a start-offset of the write-command;

a length of the write-command; and

location of the write-command in the data log.

10. A system for maintaining the order of write-commands issued to a data storage, wherein the write-commands are issued by at least one host, the system comprising:

a write-order manager to assign an order-descriptor to each write-command;

a data log associated with the issuing host to store the write-command;

a descriptor log associated to write-order manager to store the order-descriptor; and

a collating module to collate a plurality of order-descriptors from the descriptor log and their corresponding write-commands from the respective data logs to obtain an ordered write-command stream;

wherein the write-order manager comprises;

an ordering logic to assign an indicia of order to the write-command; and

a descriptor generation logic to construct the order-descriptor using the indicia of order and a metadata information for the write-command.

11. The system of claim 10, wherein the descriptor generation logic comprises a metadata extractor to extract the metadata information of the write-command.

12. The system of claim 10, wherein the write-order manager comprises an acknowledgement logic to send an acknowledgement message to the host.

13. The system of claim 10 further comprising a backup system to store the ordered write-command stream.

14. A computer readable medium comprising a program that, when executed by a processor, performs a method for maintaining the order of write-commands issued to a data storage, wherein the write-commands are issued by at least one host, the method comprising:

assigning an order-descriptor to each write-command;

storing the write-command;

storing the order-descriptor; and

collating a plurality of order-descriptors and their corresponding write-commands to obtain an ordered write-command stream;

wherein assigning the order-descriptor to a write-command comprises;

assigning an indicia of order to the write-command; and

constructing the order-descriptor using the indicia of order and metadata information for the write-command.

15. The computer readable medium of claim 14, wherein constructing the order-descriptor comprises:

receiving the write-command from the host; and

extracting the metadata information from the write-command; and

placing at least some of the metadata information into the order descriptor.

16. The computer readable medium of claim 14, wherein constructing the order-descriptor comprises:

receiving the metadata information from the host.

17. The computer readable medium of claim 14 further comprising updating a backup of the data storage using the ordered write-command stream.