Method and device for optimization of data caching
The embodiments of the present disclosure provide a computer-implemented method. The method includes caching data from a persistent storage device into a cache. The method also includes caching a physical address and a logical address of the data in the persistent storage device into the cache. The method further includes in response to receiving an access request for the data, accessing the data cached in the cache using at least one of the physical address and the logical address. The embodiments of the present disclosure also provide an electronic apparatus and a computer program product.
1. A computer-implemented method, comprising:
caching data from a persistent storage device into a cache;
caching a physical address and a logical address of the data in the persistent storage device into the cache;
caching an indicator into the cache;
setting the indicator to a positive state or a negative state to indicate whether the data is directly rewritable in the cache; and
in response to receiving an access request for the data, accessing the data cached in the cache using at least one of the physical address and the logical address, wherein accessing the data cached in the cache comprises:
in response to the access request being a rewrite request, determining whether the indicator is in the positive state or in the negative state;
in response to determining that the indicator is in the positive state, directly performing a rewrite operation on the data in the cache; and
in response to determining that the indicator is in the negative state,
caching data for rewriting in a further position in the cache, and
setting an indicator indicating whether the data for rewriting is directly rewritable to the positive state.
2. The method of claim 1 , wherein caching the physical address and the logical address into the cache comprises:
caching the physical address and the logical address using a two-dimensional hash table.
3. The method of claim 2 , wherein the two-dimensional hash table includes:
a first dimensional hash table for mapping the physical address to the logical address and the data by using the physical address as a key, and
a second dimensional hash table for mapping the logical address to the physical address by using the logical address as a key.
4. The method of claim 1 , wherein:
the logical address corresponds to one physical address or is prevented from corresponding to any physical addresses; and
the physical address corresponds to at least one of a plurality of logical addresses or is prevented from corresponding to any logical addresses.
5. The method of claim 1 , wherein setting the indicator comprises:
if the physical address corresponds to the logical address only, setting the indicator to the positive state; and
if the physical address corresponds to a plurality of logical addresses, or it is undetermined whether the physical address corresponds to the logical address only, setting the indicator to the negative state.
6. The method of claim 1 , wherein setting the indicator further comprises:
in response to performing at least one of a snapshot operation and a deduplication operation on the data in the storage device, setting the indicator to the negative state.
7. The method of claim 1 , wherein caching the data from the storage device into the cache comprises:
in response to a request for a read operation on the data, determining whether the data is cached in the cache;
in response to determining that the data is absent from the cache,
duplicating the data from the storage device into the cache; and
setting the indicator to the negative state.
8. The method of claim 1 , wherein the persistent storage device and the cache belong to a storage system which performs data storage operations on behalf of a set of external client computers; and
wherein caching the data from the persistent storage device into the cache includes:
accessing, as the data from the persistent storage device, snapshotted client data provided by the set of external client computers.
9. The method of claim 1 , wherein the persistent storage device and the cache belong to a storage system which performs data storage operations on behalf of a set of external client computers; and
wherein caching the data from the persistent storage device into the cache includes:
accessing, as the data from the persistent storage device, deduplicated client data provided by the set of external client computers.
10. An electronic apparatus, comprising:
at least one processor; and
at least one memory including computer instructions, the at least one memory and the computer instructions being configured, with the processor, to cause the electronic apparatus to:
cache data from a persistent storage device into a cache;
cache a physical address and a logical address of the data in the persistent storage device into the cache;
cache an indicator into the cache;
set the indicator to a positive state or a negative state to indicate whether the data is directly rewritable in the cache;
in response to receiving an access request for the data, access the data cached in the cache using at least one of the physical address and the logical address;
in response to the access request being a rewrite request, determine whether the indicator is in the positive state or in the negative state;
in response to determining that the indicator is in the positive state, directly perform a rewrite operation on the data in the cache; and
in response to determining that the indicator is in the negative state,
cache data for rewriting in a further position in the cache; and
set an indicator indicating whether the data for rewriting is directly rewritable to the positive state.
11. The electronic apparatus of claim 10 , wherein the at least one memory and the computer instructions are further configured, with the processor, to cause the electronic apparatus to:
cache the physical address and the logical address using a two-dimensional hash table.
12. The electronic apparatus of claim 11 , wherein the two-dimensional hash table includes:
a first dimensional hash table for mapping the physical address to the logical address and the data using the physical address as a key, and
a second dimensional hash table for mapping the logical address to the physical address by using the logical address as a key.
13. The electronic apparatus of claim 10 , wherein:
the logical address corresponds to one physical address or is prevented from corresponding to any physical addresses; and
the physical address corresponds to at least one of a plurality of logical addresses or is prevented from corresponding to any logical addresses.
14. The electronic apparatus of claim 10 , wherein the at least one memory and the computer instructions are further configured, with the processor, to cause the electronic apparatus to:
if the physical address corresponds to the logical address only, set the indicator to the positive state; and
if the physical address corresponds to a plurality of logical addresses, or it is undetermined whether the physical address corresponds to the logical address only, set the indicator to the negative state.
15. The electronic apparatus of claim 10 , wherein the at least one memory and the computer instructions are further configured, with the processor, to cause the electronic apparatus to:
in response to performing at least one of a snapshot operation and a deduplication operation on the data in the storage device, set the indicator to the negative state.
16. The electronic apparatus of claim 10 , wherein the at least one memory and the computer instructions are further configured, with the processor, to cause the electronic apparatus to:
in response to a request for a read operation on the data, determine whether the data is cached in the cache;
in response to determining that the data is absent from the cache,
duplicate the data from the storage device into the cache; and
set the indicator to the negative state.
17. A computer program product being tangibly stored on a non-volatile non-transitory computer-readable storage medium and including machine-executable instructions, the machine-executable instructions, when executed, causing a machine to perform a step of:
caching data from a persistent storage device into a cache;
caching a physical address and a logical address of the data in the persistent storage device into the cache;
caching an indicator into the cache;
setting the indicator to a positive state or a negative state to indicate whether the data is directly rewritable in the cache; and
in response to receiving an access request for the data, accessing the data cached in the cache using at least one of the physical address and the logical address, wherein accessing the data cached in the cache comprises:
in response to the access request being a rewrite request, determining whether the indicator is in the positive state or in the negative state;
in response to determining that the indicator is in the positive state, directly performing a rewrite operation on the data in the cache; and
in response to determining that the indicator is in the negative state,
caching data for rewriting in a further position in the cache, and
setting an indicator indicating whether the data for rewriting is directly rewritable to the positive state.
18. The computer program product of claim 17 , wherein caching the physical address and the logical address into the cache comprises:
caching the physical address and the logical address using a two-dimensional hash table.