How to ensure data reaches storage, bypassing memory/cache/buffered-IO?

问题

In Linux, how to ensure my system write() calls (and similar write-IO calls/variants) reach non-volatile storage, bypassing memory/cache/buffered-IO?

回答1:

See "Ensuring data reaches disk."

In short, the safest policy is O_DIRECT + fsync() at appropriate points.

回答2:

Using O_DIRECT would achieve the purpose but that can be inefficient for most applications, unless you are managing the whole file caching/buffering in your application. Typically there are two ways this is done.

1. Use O_SYNC flag while opening the file, so that the writes will block till it is written to underlying persistent storage.
2. Do the normal file operations and call fsync when you want to make sure the changes are written to storage device.

Remember if you are using mmap, then msync would be a better way to do the same.

来源：https://stackoverflow.com/questions/14385168/how-to-ensure-data-reaches-storage-bypassing-memory-cache-buffered-io