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39 lines
1.2 KiB
39 lines
1.2 KiB
dm-queue-length |
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=============== |
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dm-queue-length is a path selector module for device-mapper targets, |
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which selects a path with the least number of in-flight I/Os. |
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The path selector name is 'queue-length'. |
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Table parameters for each path: [<repeat_count>] |
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<repeat_count>: The number of I/Os to dispatch using the selected |
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path before switching to the next path. |
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If not given, internal default is used. To check |
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the default value, see the activated table. |
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Status for each path: <status> <fail-count> <in-flight> |
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<status>: 'A' if the path is active, 'F' if the path is failed. |
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<fail-count>: The number of path failures. |
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<in-flight>: The number of in-flight I/Os on the path. |
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Algorithm |
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========= |
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dm-queue-length increments/decrements 'in-flight' when an I/O is |
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dispatched/completed respectively. |
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dm-queue-length selects a path with the minimum 'in-flight'. |
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Examples |
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======== |
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In case that 2 paths (sda and sdb) are used with repeat_count == 128. |
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# echo "0 10 multipath 0 0 1 1 queue-length 0 2 1 8:0 128 8:16 128" \ |
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dmsetup create test |
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# |
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# dmsetup table |
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test: 0 10 multipath 0 0 1 1 queue-length 0 2 1 8:0 128 8:16 128 |
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# |
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# dmsetup status |
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test: 0 10 multipath 2 0 0 0 1 1 E 0 2 1 8:0 A 0 0 8:16 A 0 0
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