METHOD, APPARATUS, AND COMPUTER PROGRAM PRODUCT FOR PROVIDING CACHE SERVICE

• US 20200133867A1
• Filed: 09/17/2019
• Published: 04/30/2020
• Est. Priority Date: 10/30/2018
• Status: Active Grant

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Inventors: Jia, Ruiyong, Xu, Xinlei, Yang, Lifeng, Liu, Yousheng, Feng, Changyu
• Granted Patent: US 11,010,301 B2
• Time in Patent Office: Days
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache
• CPC Class Codes: G06F 12/0873 Mapping of cache memory to specific storage devices or parts thereof
• CPC Class Codes: G06F 12/0891 using clearing, invalidating or resetting means
• CPC Class Codes: G06F 12/1054 the data cache being concurrently physically addressed
• CPC Class Codes: G06F 12/1063 the data cache being concurrently virtually addressed
• CPC Class Codes: G06F 2212/313 In storage device
• CPC Class Codes: G06F 2212/6012 of operating mode, e.g. cache mode or local memory mode

Abstract

Techniques provide cache service in a storage system. Such techniques involve a storage cell pool, a cache and an underlying storage system. The storage cell pool includes multiple storage cells, a storage cell among the multiple storage cells being mapped to a physical address in the underlying storage system via an address mapping of the storage system. Specifically, an access request for target data at a virtual address in the storage cell pool is received, and the type of the access request is determined. The access request is served with the cache on the basis of the determined type, where the cache is used to cache data according to a format of a storage cell in the storage cell pool. The cache directly stores data in various storage cells in the pool that is visible to users, so that response speed for the access request may be increased.

Claims

1. A method for providing cache service in a storage system, the storage system comprising a storage cell pool, a cache and an underlying storage system, the storage cell pool comprising multiple storage cells, a storage cell among the multiple storage cells being mapped to a physical address in the underlying storage system via an address mapping of the storage system, the method comprising:

receiving an access request for target data at a virtual address in the storage cell pool;

determining the type of the access request, the type comprising a read request for reading the target data from the storage system and a write request for writing the target data to the storage system; and

serving the access request with the cache on the basis of the determined type, wherein the cache is used to cache data in at least one part of storage cells in the storage cell pool according to a format of a storage cell in the storage cell pool.

2. The method of claim 1, wherein serving the access request with the cache comprises:

in response to determining the access request is a read request,

obtaining the virtual address from the read request;

determining whether data corresponding to the virtual address exist in the cache or not;

in response to determining the data exist in the cache, reading the data from the cache; and

returning the read data so as to respond to the read request.

3. The method of claim 2, further comprising:

in response to determining the data do not exist in the cache,

determining a physical address of the target data in the underlying storage system on the basis of the address mapping;

reading the target data from the physical address in the underlying storage system so as to load the read target data to the cache; and

returning the read target data so as to respond to the read request.

4. The method of claim 1, further comprising:

determining candidate data to be read by a next read request on the basis of the access request; and

loading the candidate data to the cache from the underlying storage system.

5. The method of claim 4, wherein loading the candidate data to the cache from the underlying storage system comprises:

obtaining a candidate address of the candidate data in the storage cell pool;

determining a physical address in the underlying storage system which corresponds to the candidate address on the basis of the address mapping; and

reading the candidate data from the physical address of the underlying storage system so as to load the read candidate data to the cache.

6. The method of claim 1, wherein serving the access request with the cache comprises:

in response to determining the access request is a write request,

writing the target data to the cache; and

setting a state of the target data in the cache to “

dirty”

so as to indicate the target data in the cache are not yet flushed to the underlying storage system.

7. The method of claim 6, further comprising:

determining a physical address in the underlying storage system which corresponds to the virtual address on the basis of the address mapping; and

writing the target data to the physical address in the underlying storage system.

8. The method of claim 7, wherein writing the target data to the physical address in the underlying storage system comprises:

flushing the target data in the cache to the physical address in the underlying storage system; and

setting the state to “

clean”

so as to indicate the target data in the cache have been flushed to the underlying storage system.

9. The method of claim 7, wherein the storage system further comprises a peer cache, the peer cache being used to cache data in at least one part of storage cells in the storage cell pool according to a format of a storage cell in the storage cell pool, the method further comprising:

synchronizing the target data with the peer cache; and

setting a peer state of the synchronized target data in the peer cache to “

dirty”

so as to indicate the synchronized target data in the peer cache are not yet flushed to the underlying storage system.

10. The method of claim 9, further comprising:

setting the peer state to “

clean”

in response to the target data in the cache having been flushed to the underlying storage system.

11. An apparatus for providing cache service in a storage system, the storage system comprising a storage cell pool, a cache and an underlying storage system, the storage cell pool comprising multiple storage cells, a storage cell among the multiple storage cells being mapped to a physical address in the underlying storage system via an address mapping of the storage system, the apparatus comprising:

at least one processor;

a volatile memory; and

a memory coupled to the at least one processor and having instructions stored thereon, the instructions, when executed by the at least one processor, causing the apparatus to perform acts comprising;

receiving an access request for target data at a virtual address in the storage cell pool;

determining the type of the access request, the type comprising a read request for reading the target data from the storage system and a write request for writing the target data to the storage system; and

serving the access request with the cache on the basis of the determined type, wherein the cache is used to cache data in at least one part of storage cells in the storage cell pool according to a format of a storage cell in the storage cell pool.

12. The apparatus of claim 11, wherein serving the access request with the cache comprises:

in response to determining the access request is a read request,

obtaining the virtual address from the read request;

determining whether data corresponding to the virtual address exist in the cache or not;

in response to determining the data exist in the cache, reading the data from the cache; and

returning the read data so as to respond to the read request.

13. The apparatus of claim 12, wherein the acts further comprise:

in response to determining the data do not exist in the cache,

determining a physical address of the target data in the underlying storage system on the basis of the address mapping;

reading the target data from the physical address in the underlying storage system so as to load the read target data to the cache; and

returning the read target data so as to respond to the read request.

14. The apparatus of claim 11, wherein the acts further comprise:

determining candidate data to be read by a next read request on the basis of the access request; and

loading the candidate data to the cache from the underlying storage system.

15. The apparatus of claim 14, wherein loading the candidate data to the cache from the underlying storage system comprises:

obtaining a candidate address of the candidate data in the storage cell pool;

determining a physical address in the underlying storage system which corresponds to the candidate address on the basis of the address mapping; and

reading the candidate data from the physical address of the underlying storage system so as to load the read candidate data to the cache.

16. The apparatus of claim 11, wherein serving the access request with the cache comprises:

in response to determining the access request is a write request,

writing the target data to the cache; and

setting a state of the target data in the cache to “

dirty”

so as to indicate the target data in the cache are not yet flushed to the underlying storage system.

17. The apparatus of claim 16, wherein the acts further comprise:

determining a physical address in the underlying storage system which corresponds to the virtual address on the basis of the address mapping; and

writing the target data to the physical address in the underlying storage system.

18. The apparatus of claim 17, wherein writing the target data to the physical address in the underlying storage system comprises:

flushing the target data in the cache to the physical address in the underlying storage system; and

setting the state to “

clean”

so as to indicate the target data in the cache have been flushed to the underlying storage system.

19. The apparatus of claim 17, wherein the storage system further comprises a peer cache, the peer cache being used to cache data in at least one part of storage cells in the storage cell pool according to a format of a storage cell in the storage cell pool, the method further comprising:

synchronizing the target data with the peer cache; and

setting a peer state of the synchronized target data in the peer cache to “

dirty”

so as to indicate the synchronized target data in the peer cache are not yet flushed to the underlying storage system.

20. The apparatus of claim 19, wherein the acts further comprise:

setting the peer state to “

clean”

in response to the target data in the cache having been flushed to the underlying storage system.

21. A computer program product having a non-transitory computer readable medium which stores a set of instructions to provide cache service in a storage system which includes a storage cell pool, a cache and an underlying storage system, the storage cell pool including multiple storage cells, a storage cell among the multiple storage cells being mapped to a physical address in the underlying storage system via an address mapping of the storage system;

the set of instructions, when carried out by computerized circuitry, causing the computerized circuitry to perform a method of;

receiving an access request for target data at a virtual address in the storage cell pool;

determining the type of the access request, the type comprising a read request for reading the target data from the storage system and a write request for writing the target data to the storage system; and

serving the access request with the cache on the basis of the determined type, wherein the cache is used to cache data in at least one part of storage cells in the storage cell pool according to a format of a storage cell in the storage cell pool.