Log-Based Storage Indexing for Sequential Write Media
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Solution Overview
Problem
Shingled magnetic recording (SMR) techniques and other sequential write media face challenges in non-sequential data access, requiring inefficient methods like tracking all data writes or reading entire data sets for content determination, which is burdensome and inefficient.
Innovation Solution
A log-based storage design that generates write and deletion logs to serve as data location indexes, allowing for sequential writing and efficient tracking and indexing of data, enabling random reads and efficient deletion by adding omission references in subsequent writes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If data is written to SMR devices in a non-sequential fashion, then storage density can be increased, but data tracking and indexing become inefficient and burdensome
Solution Approach 1:
The patent divides the data storage structure into two distinct segments: a log structure for sequential write tracking and a traditional data storage area. The log contains metadata entries that segment and index the data, enabling efficient tracking without requiring non-sequential writes to the physical media.
Solution Approach 2:
The patent introduces a log as an intermediary structure between the data storage device and the data itself. This log contains metadata entries that act as mediators to track and index data locations, eliminating the need to scan entire data sets or track every individual write operation.
2Measurement precision
If all data is read back to determine contents, then data can be located, but the process becomes burdensome and inefficient
Solution Approach 1:
The patent performs preliminary indexing action by writing metadata entries to the log at the time of data storage. These entries record the location and characteristics of data blocks, enabling rapid retrieval without requiring time-consuming scans of the entire data set later.
Solution Approach 2:
The patent creates a copy of the data location information in the form of metadata entries within the log. Instead of reading the actual data contents to determine location, the system reads these metadata copies that point to the data locations, significantly reducing retrieval time.
3Ease of manufacture
If sequential writing is enforced, then write operations are simplified, but random access and deletion become more difficult
Solution Approach 1:
The patent introduces dynamic indexing capability through the log structure that maintains metadata entries updated with each sequential write. This dynamic metadata structure enables random access and efficient deletion operations despite the sequential nature of physical writes, as the metadata can be read and processed in any order.
Solution Approach 2:
The patent adds a new dimension to the storage system by introducing metadata entries that provide an additional layer of information about data locations and characteristics. This extra dimension enables random access and efficient deletion without changing the sequential write mechanism of the physical media.
4Reliability
If data deletion is performed by tracking all writes, then deletion accuracy is maintained, but system complexity and overhead increase
Solution Approach 1:
The patent extracts the deletion tracking function from the complex task of monitoring all data writes. By using the log's metadata entries that record data locations and characteristics, the system can independently perform accurate deletion without needing to track every individual write operation, reducing system complexity.
Solution Approach 2:
The patent enables efficient deletion by discarding the need to maintain complex write tracking state. The metadata entries in the log can be read and processed to identify data for deletion, and the system can recover from deletion operations using the same metadata structure, simplifying the overall deletion process.
Data Source
AI summary
Techniques for implementing a log-based storage scheme upon data storage devices are described herein. A data storage device is initialized by writing an identifying record. For each portion of data to be written to the drive, a first record including information regarding the anticipated nature of the portion of data is written prior to the data. The data is then written as a second record that includes at least the raw data as well as integrity verification information. A third record is stored following the second record, and includes an accounting and/or index of the data successfully written in the second record. On sequentially written devices, the information in the first stored record may be used to locate the third record, which in turn may be used to record data in the second record as well as the location of a first record of another portion of data.