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Testing Multiple Drives for Consistency for a RAID or Similar

diglloydTools

Among its many features, diglloydTools DiskTester offers a run-area-test command that can be used for relatively fast characterization of drive performance across its capacity. The results can be graphed to get a good idea of the drive performance.

For example, suppose a high performance RAID is envisioned: one laggard can cut the performance, since the slowest drive determines the peak speed.

As shown below, 8 samples were tested, and one of those eight is a significant laggard; this slower drive is best set aside as a cold spare or backup drive.

While DiskTester can test any number of drives simultaneously (via command line), testing should take care not to saturate the bandwidth; for example four fast hard drives can demand almost all of the Thunderbolt v1 bandwidth, and other devices on the bus could suck up bandwidth, disturbing the results.

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Click for larger graph.

diglloydTools DiskTester: performance across volume capacity for eight drives
disktester run-area-test --iterations 5 --test-size 4G --delta-percent 5

MacPerformanceGuide.com
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