Method and apparatus for retrieving data
AssigneeKoninklijke Philips Electronics N. V.
InventorStephen Cumpson
Life of this patent
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Abstract
The invention relates to a method of caching data stored in allocation units of a memory (102), preferably a harddisk drive system, of which retrieval incurs a performance penalty. An example of this is data in a spare sector (215), located in a spare area (210) on the hard disk platter (200). The cache memory (103) is, however, a precious commodity. The need for memory space may be reduced by only caching data in spare sectors in which data belonging to a file that is retrieved is stored. Also the impact of other kinds of causes of performance penalties may be solved in this way, like those caused by soft defects and fragmentation of files.
Claims9
A method of retrieving data requested by a host from a first memory divided into allocation units, the method being characterized in that it comprises the steps of:
- (a) determining in which allocation units the requested data is stored;
- (b) searching a list of references to allocation units to determine whether the list comprises a reference to at least one of the allocation units determined in the previous step;
- (c) when a reference to at least one allocation unit determined in the first step is comprised in the list, storing a first part of the data stored in the at least one allocation unit in a second memory;
- and
- (d) retrieving the requested data, wherein the first part of the requested data is retrieved from the second memory and a second part of the requested data is retrieved from the first memory, the second part of the requested data being complementary to the first part of the requested data.
An apparatus for retrieving data requested by a host from a first memory, the apparatus comprising:
- (a) means for receiving data from the first memory, the first memory being divided into allocation units;
- (b) a second memory;
- and
- (c) a central processing unit;
- characterized in that the central processing unit is conceived to:
- (d) determine in which allocation units the requested data is stored;
- (e) search a list of references to allocation units to determine whether the list comprises a reference to at least one of the allocation units in which the requested data is stored;
- (f) when at least one allocation unit in which the requested data is stored is comprised in the list, store the data stored in the at least one allocation unit in a second memory;
- and
- (g) retrieve the requested data, wherein a first part of the requested data stored in the second memory is retrieved from the second memory and a second part of the requested data is retrieved from the first memory, the second part of the requested data being complementary to the first part of the requested data.
A system for reproducing audio-visual information, comprising the apparatus as claimed in 6 and the first memory.
Dependencies are inferred from the claim text.