Cache and disk management method, and a controller using the method
A cache and disk management method is provided. In the cache and disk management method, a command to delete all valid data stored in a cache, or specific data corresponding to a part of the valid data may be transmitted to a plurality of member disks. That is, all of the valid data or the specific data may exist in the cache only, and may be deleted from the plurality of member disks. Accordingly, the plurality of member disks may secure more space, an internal copy overhead may be reduced, and more particularly, solid state disks may achieve better performance.
1. A method of managing a cache and a plurality of member disks, the method comprising:
searching for target data in the cache in response to a request from a host to read the target data;
caching, from the plurality of member disks, the target data in the cache based on a result of the search; and
transmitting, to the plurality of member disks, a command to delete the target data from the plurality of member disks in response to the caching of the target data.
2. The method of claim 1 , wherein the transmitting comprises transmitting, to the plurality of member disks, the delete command based on a first delete policy to transmit a command to delete from the plurality of member disks all valid data stored in the cache, or a second delete policy to transmit a command to delete from the plurality of member disks a part of the valid data stored in the cache.
3. The method of claim 1 , further comprising:
setting a state of the cached target data depending on whether the delete command is transmitted.
4. The method of claim 1 , wherein the cached target data is used as a new member of a parity group.
5. The method of claim 1 , further comprising:
transmitting, to the host, found target data when the target data is found in the cache.
6. The method of claim 1 , wherein the plurality of member disks corresponds to a solid state disk, and the cache corresponds to a write-back cache.
7. The method of claim 1 , wherein the searching comprises searching for the target data in the cache, using one of the group consisting of direct mapping, fully associative mapping, and set-associative mapping.
8. The method of claim 3 , wherein the state of the cached target data indicates whether the delete command is transmitted, or whether the cached target data is cached from the plurality of member disks.
9. A method of managing a cache and a plurality of member disks, the method comprising:
caching target data in the cache in response to a request from a host to write the target data; and
transmitting, to the plurality of member disks, a command to delete the target data from the plurality of member disks in response to the caching of the target data.
10. The method of claim 9 , wherein the caching comprises caching the target data without a replacement taking place in the cache when the target data is not pre-stored in the cache, and the transmitting comprises transmitting the delete command after the target data is cached.
11. The method of claim 9 , further comprising:
setting a state of the cached target data depending on whether the delete command is transmitted.
12. The method of claim 9 , wherein the caching comprises updating pre-stored target data when the target data is pre-stored in the cache, and the transmitting comprises transmitting the delete command when the target data is stored in the plurality of member disks.
13. The method of claim 9 , wherein the caching comprises writing back, to the plurality of member disks, victim data according to a replacement before the target data is cached when the target data is not pre-stored in the cache, and the replacement takes place in the cache.
14. The method of claim 9 , wherein the caching comprises writing back, to the plurality of member disks, victim data according to a replacement before the target data is cached depending on whether the victim data is stored in the plurality of member disks when the target data is not pre-stored in the cache, and the replacement takes place in the cache.
15. The method of claim 9 , wherein the caching comprises caching a parity to be updated based on the target data.
16. The method of claim 15 , wherein the transmitting comprises transmitting a command to delete the parity to the plurality of member disks.
17. The method of claim 13 , wherein the caching comprises:
caching a parity to be updated based on the target data; and
writing back, to the plurality of member disks, the victim data according to the replacement, and a victim parity corresponding to the victim data before the target data and the parity are cached.
18. The method of claim 15 , further comprising:
mirroring the cached target data and the cached parity to the cache.
19. A non-transitory computer-readable medium comprising a program for instructing a computer to perform the method of claim 1 .
20. A controller, comprising:
a searching unit to search for target data in a cache in response to a request from a host to read the target data;
a caching unit to cache, from a plurality of member disks, the target data in the cache based on a result of the search; and
a delete command transmitting unit to transmit, to the plurality of member disks, a command to delete the target data from the plurality of member disks in response to the caching of the target data.
21. The controller of claim 20 , wherein the caching unit caches the target data in the cache in response to a request to write the target data.