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At the file pool (or even the single file) level, data access settings can be configured to optimize data access for the type of application accessing it. Data can be optimized for concurrent, streaming, or random access. Each of these settings changes how data is laid out on disk and how it is cached.
Data access setting | Description | On disk layout | Caching |
Concurrency | Optimizes for current load on the cluster, featuring many simultaneous clients. This setting provides the best behavior for mixed workloads. | Stripes data across the minimum number of drives required to achieve the data protection setting configured for the file. | Moderate prefetching |
Streaming | Optimizes for high-speed streaming of a single file. For example, to enable rapid reading with a single client. | Stripes data across a larger number of drives. | Aggressive prefetching |
Random | Optimizes for unpredictable access to the file by performing almost no cache prefetching. | Stripes data across the minimum number of drives required to achieve the data protection setting configured for the file. | Little to no prefetching |
As the settings indicate, the Random data access setting performs little to no read-cache prefetching to avoid wasted disk access. This setting works best for small files (< 128 KB) and large files with random small block accesses. Streaming access works best for sequentially read medium to large files. This access pattern uses aggressive prefetching to improve overall read throughput, and on disk layout it spreads the file across many disks to optimize access. Concurrency (the default setting for all file data) access is the middle ground with moderate prefetching. Use this setting for file sets with both random and sequential access.