US 6,587,919 B2 · System and method for disk mapping and data retrieval

Abstract

A data storage system includes data storage and a record locator data structure in random access memory. The record locator data structure includes entries having different lengths. For locating variable-length data records in the data storage, for example, at least some but not all of the entries have a data-length portion indicating data length of a respective data record of the entry when the data length of the respective data record fails to match an expected data length. Each entry, for example, has a fixed length portion including an indication of whether or not the entry has a data-length portion, the fixed length portions are stored sequentially in a first region of address locations of the random access memory, and the data-length portions are stored sequentially in a second region of address locations of the random access memory.

Claims42

Dependent claims

A data storage system comprising data storage, random-access memory, and at least one processor responsive to data storage access requests for access to data stored in the data storage, each data storage access request specifying at least one data record of a logical track of data records, the data records of the logical track including variable-length data records, the data processor being programmed to access a record locator data structure in the random-access memory for locating a data storage area in the data storage allocated for storing data of the data record, the record locator data structure containing respective entries for data records having data stored in the data storage, at least some but not all of the entries having a data-length portion indicating data length of the data record of the entry when the data length of the record of the entry fails to match an expected data length.

A data storage system comprising data storage, random-access memory, and at least one processor responsive to data storage access requests for access to data stored in the data storage, each data storage access request specifying at least one data record of a logical track of data records, the data processor being programmed to access a record locator data structure in the random-access memory for locating a data storage area in the data storage allocated for storing data of the data record, the record locator data structure containing respective entries for data records having data stored in the data storage, each entry including a fixed-length portion, and at least some but not all of the entries having respective variable-length portions, the fixed-length portions being stored sequentially in a first region of address locations of the random-access memory, and the variable-length portions being stored sequentially in a second region of address locations of the random-access memory.

A method of maintaining a record locator data structure in random access memory of a data storage system also having data storage and at least one processor responsive to data storage access requests for access to data stored in the data storage, each data storage access request specifying at least one data record of a logical track of data records, the data records of the logical track including variable-length data records, the data processor being programmed to access the record locator data structure in the random-access memory for locating a data storage area in the data storage allocated for storing data of the data record, the record locator data structure containing respective entries for data records having data stored in the data storage, at least some but not all of the entries having a data-length portion indicating data length of the data record of the entry, the method including updating the record locator data structure to include a new entry for a new data record by:

(a) establishing an expected data length for the new data record;
(b) comparing the data length of the new data record to the expected data length for the new data record, and
(i) if the data length of the new data record does not match the expected data length of the new data record, storing a data-length portion indicating the data length of the new data record of the new entry;
and
(ii) if the data length of the new data record matches the expected data length of the new data record, not storing a data-length portion indicating the data length of the new data record of the new entry.

2 more elements

A method of maintaining a record locator data structure in random access memory of a data storage system also having data storage and at least one processor responsive to data storage access requests for access to data stored in the data storage, each data storage access request specifying at least one count-key-data (CKD) record of a logical track of CKD records, the data processor being programmed to access the record locator data structure in the random-access memory for locating a data storage area in the data storage allocated for storing data of the CKD record, the record locator data structure containing entries for the CKD records having data stored in the data storage, at least some but not all of the entries having a respective record modifier portion, the method including updating the record locator data structure to include a new entry for a new CKD record by:

(a) establishing an expected count for the new CKD record;
(b) comparing the count of the new CKD record to the expected count for the new CKD record, and
(i) if the count of the new CKD record does not match the expected count of the new CKD record, storing a record modifier portion indicating the count of the new CKD record of the new entry;
and
(ii) if the count of the new CKD record matches the expected count of the new CKD record, not storing a record modifier portion indicating the count of the new CKD record of the new entry.

2 more elements

A method of maintaining a record locator data structure in random access memory of a data storage system also having data storage and at least one processor responsive to data storage access requests for access to data stored in the data storage, each data storage access request specifying at least one data record of a logical track of data records, the data processor being programmed to access the record locator data structure for locating a data storage area in the data storage allocated for storing data of the data record, the record locator data structure containing entries for data records having data stored in the data storage, each entry including a fixed-length portion, and at least some but not all of the entries having respective variable-length portions, the method including updating the record locator data structure to include a new entry for a new data record by:

(a) determining whether or not to include a variable length portion in the new entry for the new data record, and
(b) setting a value in the fixed-length portion of the new entry indicating whether or not the new entry includes a variable-length portion.

A method of maintaining a record locator data structure in random access memory of a data storage system also having data storage and at least one processor responsive to data storage access requests for access to data stored in the data storage, each data storage access request specifying at least one data record of a logical track of data records, the data processor being programmed to access the record locator data structure for locating a data storage area in the data storage allocated for storing data of the data record, the record locator data structure containing respective entries for data records having data stored in the data storage, each entry including a fixed-length portion, and at least some but not all of the entries having respective variable-length portions, the method including updating the record locator data structure to include a new entry for a new data record by:

(a) determining whether or not the new entry is to have a variable-length portion, and
(b) storing a fixed-length portion for the new data record in a next address location in a first region of address locations of the random-access memory, and if the new entry is to have a variable-length portion, storing the variable-length portion of the new entry in a next address location in a second region of address locations of the random-access memory.

Dependencies are inferred from the claim text.

System and method for disk mapping and data retrieval

Life of this patent

System and method for disk mapping and data retrieval

Life of this patent

Abstract

Claims42