SMR Disk Access Efficiency via Server-Side Write Pointer Caching
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Solution Overview
Problem
The efficiency of accessing a shingled magnetic recording (SMR) disk by a server is low due to the need for repeated use of open zone and report zone instructions to obtain write pointer information before each data operation.
Innovation Solution
A method where a server caches write pointer information for SMR disks, allowing it to generate and send data operation instructions without needing to send open zone and report zone instructions each time, thereby improving access efficiency by storing and updating write pointer information in the cache.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the server sends open zone instruction and report zone instruction before each data operation to obtain write pointer information, then the SMR disk can correctly perform sequential write operations, but the access efficiency of the server is reduced due to repeated instruction exchanges
Solution Approach 1:
The server performs preliminary actions by opening zones and obtaining write pointer information before actual data operations are needed. The write pointer information is cached and reused for multiple subsequent write operations within the same zone, eliminating the need to repeatedly send open zone and report zone instructions. This preliminary action resolves the contradiction by preparing necessary information in advance that can be reused, thereby improving access efficiency while maintaining correct sequential write operations.
Solution Approach 2:
The server creates a copy of the write pointer information and stores it in local cache memory. Instead of repeatedly querying the SMR disk for the same write pointer information, the server uses the cached copy for multiple data operations. This copying approach maintains the reliability of sequential write operations while significantly improving access efficiency by reducing repeated instruction exchanges with the disk.
2Loss of information
If the server frequently exchanges instructions with the SMR disk to maintain write pointer information, then the write pointer can be kept up-to-date, but the time consumed for each data operation increases
Solution Approach 1:
The server performs preliminary actions by obtaining and caching write pointer information before actual data operations. This allows the server to have the necessary information ready in advance, reducing the time consumed during actual data operations while maintaining information accuracy through periodic updates when zones are closed or reopened.
Solution Approach 2:
The server creates and maintains local copies of write pointer information in cache memory. These copies are updated only when necessary (when zones are closed or reopened), rather than being frequently refreshed. This approach minimizes the time lost to instruction exchanges while ensuring the cached information remains accurate for the duration of zone validity.
3Adaptability or versatility
If the server uses five zone instructions (open zone, finish zone, close zone, report zone, reset write pointer) according to the standard, then the SMR disk operations are standardized and compatible, but the complexity of the access protocol increases
Solution Approach 1:
The server extracts and separates the zone management functions from the data operation functions. By caching write pointer information and handling zone opening/closing independently, the server simplifies the access protocol for routine data operations. The five zone instructions are still used when necessary for standard compliance, but routine operations can proceed with simpler cached information, reducing the perceived complexity while maintaining full standard compatibility.
Solution Approach 2:
The server introduces a caching mechanism as an intermediary layer between the application layer and the SMR disk. This cache absorbs the complexity of zone management instructions, translating high-level data operations into the necessary zone instructions only when needed. This intermediary approach maintains standard compliance and compatibility while shielding the application from protocol complexity.
Data Source
AI summary
A method for a server to access a shingled magnetic recording (SMR) disk includes: receiving, by the server, a data operation request, where the data operation request includes address information of target data; determining, according to the address information, a target storage zone in the SMR disk and that corresponds to the target data; determining that there is write pointer information of the target storage zone in a cache, and obtaining the write pointer information from the cache, where the write pointer information is address information of latest stored data in the target storage zone; generating a data operation instruction according to the write pointer information and the address information of the target data, where the data operation instruction is used to perform an operation on the target data; and sending the data operation instruction to the SMR disk.