The CFQ "low latency" mode
Posted Oct 13, 2009 0:22 UTC (Tue) by giraffedata
In reply to: The CFQ "low latency" mode
Parent article: The CFQ "low latency" mode
OK, I'll buy that. Letting the disk sit idle can improve the throughput capacity for a limited workload like that (limited not because there are times when there is no work available but because there are only two streams and each apparently doesn't want to have more than one I/O at a time outstanding).
What I was thinking is that when people ask about disk throughput (capacity), it's usually on a system that drives the disk a lot harder than that -- i.e. the disk's basic capacity is in question. That means
requesters throw large amounts of I/O at the disk and the speed is then determined by how quickly the disk can move the I/Os through. In the A-B scenario you describe, I would ask about the disk's response time, not its throughput, because it's the waiting for a response that governs the speed of this system.
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