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Chapter 11. Read-ahead Settings
RBD supports read-ahead/prefetching to optimize small, sequential reads. This should normally be handled by the guest OS in the case of a VM, but boot loaders may not issue efficient reads. Read-ahead is automatically disabled if caching is disabled.
rbd readahead trigger requests
- Description
- Number of sequential read requests necessary to trigger read-ahead.
- Type
- Integer
- Required
- No
- Default
-
10
rbd readahead max bytes
- Description
- Maximum size of a read-ahead request. If zero, read-ahead is disabled.
- Type
- 64-bit Integer
- Required
- No
- Default
-
512 KiB
rbd readahead disable after bytes
- Description
- After this many bytes have been read from an RBD image, read-ahead is disabled for that image until it is closed. This allows the guest OS to take over read-ahead once it is booted. If zero, read-ahead stays enabled.
- Type
- 64-bit Integer
- Required
- No
- Default
-
50 MiB
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