Ensuring write operation consistency using multiple storage devices
View Patent ↗Relatively small capacity solid-state storage devices (SSD) are combined with larger capacity magnetic disk storage devices for storing storage block write data to ensure data consistency. Write operations are stored in a sequential write buffer in an SSD to guarantee the storage of write data and then copied from the sequential write buffer to the destination address in a magnetic disk storage device. The sequential write buffer store write data in locations corresponding to the order of receipt of write operations. Write data from the sequential write buffer is transferred to the magnetic disk storage device in the same order and a checkpoint index is frequently updated to indicate the completion of some transfers. During system initialization, the most recent value of the checkpoint index is retrieved and used as a starting location for transferring write data from the sequential write buffer to the magnetic disk storage device.
1. A method of storing data to a data storage device, the method comprising:
receiving a write operation including write data and a destination address;
storing a page in a sequential write buffer included in a first non-volatile storage device guaranteeing data consistency and durability, wherein the page includes the destination address and the write data; and
upon completing the storage of the page in the sequential write buffer, transferring at least the write data from the page to a second non-volatile storage device that does not guarantee data consistency and/or durability.
2. The method of claim 1 , wherein the first non-volatile storage device includes a solid-state storage device that guarantees data consistency.
3. The method of claim 1 , wherein the second non-volatile storage device includes a magnetic disk storage device.
4. The method of claim 1 , wherein the second non-volatile storage device has a data capacity larger than the first non-volatile storage device.
5. The method of claim 1 , wherein at least the write data is stored in the destination address in the second non-volatile storage device.
6. The method of claim 5 , wherein the page is stored in the sequential write buffer in a storage location indicative of the order of the write operation relative to previously received write operations.
7. The method of claim 1 , comprising:
determining if a checkpoint has been reached; and
in response to the determination that the checkpoint has been reached, updating a checkpoint index value.
8. The method of claim 7 , wherein the checkpoint index value is stored in the first non-volatile storage device.
9. The method of claim 7 , wherein determining if the checkpoint has been reached comprises determining if a predefined quantity of data has been transferred to the second non-volatile storage device since a previous checkpoint.
10. The method of claim 7 , wherein determining if the checkpoint has been reached comprises determining if a predefined quantity of pages has been transferred to the second non-volatile storage device since a previous checkpoint.
11. The method of claim 7 , wherein determining if the checkpoint has been reached comprises determining if a predefined quantity of time has passed since a previous checkpoint.
12. A method of storing data to a data storage device, the method comprising:
accessing a previously stored checkpoint index value;
setting a write transfer index to the previously stored checkpoint index value;
selecting a page at a location in a sequential write buffer associated with the write transfer index, wherein the sequential write buffer is included in a first non-volatile storage device guaranteeing data consistency;
determining if the selected page has previously been transferred to a second non-volatile storage device that does not guarantee data consistency; and
in response to the determination that the selected page may not have been transferred to the second non-volatile storage device, transferring at least the write data from the selected page to the second non-volatile storage device.
13. The method of claim 12 , comprising:
following the transfer of at least the write data from the selected page, setting the write transfer index to a second location in the sequential write buffer; and
repeating the steps of selecting, determining, and transferring with the write transfer index set to the second location.
14. The method of claim 12 , wherein the location of the selected page in the sequential write buffer is indicative of a relative order of receipt of a corresponding write operation with respect to other write operations.
15. The method of claim 12 , wherein the selected page includes a destination address and transferring at least the write data from the selected page comprises storing the write data at the destination address in the second non-volatile storage device.
16. The method of claim 12 , wherein determining if the selected page has previously been transferred to the second non-volatile storage device comprises:
comparing an attribute of the selected page with an attribute of a previous page in the sequential write buffer.
17. The method of claim 12 , wherein in response to the determination that the selected page has been previously transferred to the second non-volatile storage device, waiting for the receipt of a write operation.
18. The method of claim 12 , wherein the first non-volatile storage device includes a solid-state storage device that guarantees data consistency.
19. The method of claim 12 , wherein the second non-volatile storage device includes a magnetic disk storage device.
20. The method of claim 12 , wherein the second non-volatile storage device has a data capacity larger than the first non-volatile storage device.
21. The method of claim 13 , comprising:
determining if a checkpoint has been reached; and
in response to the determination that the checkpoint has been reached, updating the previously stored checkpoint index value with a value based on the location of the selected page in the sequential write buffer.
22. The method of claim 21 , wherein the checkpoint index value is stored in the first non-volatile storage device.