Disc device provided with primary and secondary caches
AssigneeNEC Corporation
InventorShun Kurita
Life of this patent
Estimating the term…
Abstract
In a disc device according to the present invention, when a controller 2 abandons a block from a cache memory 4 used as a primary cache, it is determined whether or not the number of readings of data in the block exceeds the specified number of times. Only when the number of readings exceeds the specified number of times, the block is written into an SSD 8 used as a secondary cache. When the number of readings is equal to or smaller than the specified number of times, the block is rewritten into an HDD 7.
Claims8
A disc device comprising:
- a disc;
- a primary cache that records a copy of a part of data recorded in the disc therein;
- a secondary cache formed of an SSD, the secondary cache recording a copy of a part of data recorded in the disc therein;
- a control unit, wherein
- a block is selected to be abandoned in the primary cache in order to make a blank area in the primary cache, and in the case where the number of readings of the block selected to be abandoned in the primary cache exceeds a threshold which is a value representing a plurality of times, the control unit records the block in the secondary cache, and
- at read request,
- when data to be read exists in the primary cache, the control unit returns the data to be read in the primary cache to a requester, and
- when the data to be read does not exist in the primary cache and exists in the secondary cache, the control unit writes a block containing the data to be read that exists in the secondary cache into the primary cache and then, returns the data to be read to the requester;
- and
- a management information list part for storing a number of readings that represent a number of readings of the block in a primary cache, and a flag that represents whether or not the number of readings of the block exceeds the threshold;
- wherein,
- the control unit determines whether or not a number of readings of a block selected to be abandoned in a primary cache exceeds the threshold, based on the flag of the management information list part.
A secondary cache utilizing method in a disc device including a disc, a primary cache that records a copy of a part of data recorded in the disc therein and a secondary cache formed of an SSD, the secondary cache recording a copy of a part of data recorded in the disc therein, wherein
- a block is selected by a control unit to be abandoned in the primary cache in order to make a blank area in the primary cache and in the case where the number of readings of the block selected to be abandoned in the primary cache exceeds a threshold which is a value representing a plurality of times, the control unit records the block in the secondary cache, and
- at read request,
- when data to be read exists in the primary cache, the control unit returns the data to be read in the primary cache to a requester, and
- when the data to be read does not exist in the primary cache and exists in the secondary cache, the control unit writes a block containing the data to be read that exists in the secondary cache into the primary cache and then, returns the data to be read to the requester;
- storing, by a management information list part, a number of readings that represent a number of readings of the block in a primary cache, and a flag that represents whether or not the number of readings of the block exceeds the threshold;
- and
- determining, by the control unit, whether or not a number of readings of a block selected to be abandoned in a primary cache exceeds the threshold, based on the flag of the management information list part.
A non-transitory computer-readable recording medium having a program for allowing a CPU mounted in a disc device including a disc, a primary cache that records a copy of a part of data recorded in the disc therein and a secondary cache formed of an SSD, the secondary cache recording a copy of a part of data recorded in the disc, the CPU functioning as a control unit, wherein
- a block is selected to be abandoned in the primary cache in order to make a blank area in the primary cache, and in the case where the number of readings of the block selected to be abandoned in the primary cache exceeds a threshold which is a value representing a plurality of times, the control unit records the block in the secondary cache, and
- at read request,
- when data to be read exists in the primary cache, the control unit returns the data to be read in the primary cache to a requester, and
- when the data to be read does not exist in the primary cache and exists in the secondary cache, the control unit writes a block containing the data to be read that exists in the secondary cache into the primary cache and then, returns the data to be read to the requester;
- storing, by a management information list part, a number of readings that represent a number of readings of the block in a primary cache, and a flag that represents whether or not the number of readings of the block exceeds the threshold;
- and
- determining, by the control unit, whether or not a number of readings of a block selected to be abandoned in a primary cache exceeds the threshold, based on the flag of the management information list part.
Dependencies are inferred from the claim text.