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Mirrored Disk Scheduling Methods with a Non-Volatile Shared Cache
| Content Provider | CiteSeerX |
|---|---|
| Author | Thomasian, Er Liu, Chang |
| Abstract | Mirrored disks were a popular paradigm to attain high data availability, as well as perfor-mance, even before they were classified as RAID1. Caching of data blocks to be written to disk at first in non-volatile storage (NVS) can be used to further improve mirrored disk performance. Such blocks can be destaged asynchronously, thus allowing read requests to be processed at a higher priority than destage requests. In addition blocks can be destaged in batches optimized with respect to disk layout. A mirrored disk scheduling method proposed by Polyzois et al. always makes one disk available for processing read requests, while the other disk processes a write batch according to the CSCAN algorithm. Polyzois ’ method can be improved by: (i) eliminating the forced idleness by processing write requests individually; (ii) using an SATF-based scheduling method or even an exhaustive search for smaller batch sizes; (iii) introducing a threshold for the number of read requests, which when attained results in deferring the process-ing of write batches. We also consider a modification to SATF, where read requests are given priority to write requests, unless the latter can be processed much more efficiently than read requests. Head-of-the-line (HOL) priority queueing with higher priority for read requests than write requests is inferior to SATF, since it processes requests from both queues in FCFS order. We report on simulation results of the four schemes and show that the new method outperforms Polizois ’ method, which is even outperformed by the HOL priority method. Modified SATF policy outperforms all other methods in terms of throughput and response time. |
| File Format | |
| Access Restriction | Open |
| Subject Keyword | Read Request Non-volatile Shared Cache Mirrored Disk Scheduling Method Write Request Write Batch Popular Paradigm New Method Outperforms Polizois Method Exhaustive Search Mirrored Disk Performance Satf-based Scheduling Method Non-volatile Storage Polyzois Method Addition Block Destage Request Cscan Algorithm Hol Priority Method Data Block Fcfs Order High Data Availability Mirrored Disk Modified Satf Policy Outperforms Batch Size |
| Content Type | Text |
