Preventing Read Cache Access from Linux

Question

AFAIK reads the entire disk on linux, falling into the page cache.

Is there a way to prevent reading (performed by the backup process) in order to enter the page cache?

Imagine:

• The server is working fine, since most operations do not need to touch the disk, as there is enough memory available.
• Now the backup process begins and reads a lot. Read bytes fall into memory (cache page), although no one wants to read the same bytes in the next hours.
• Backup data fills the memory, and more important pages from the cache are deleted.
• Server performance degrades as more operations need to be touched on the disk because the corresponding pages have been removed from the cache.

My preferred solution:

• Tell linux that the reads performed by the backup process do not need to be cached in the page.

Answer 1

• if you use rsync , there is a flag --drop-cacheaccording to this question
• nocache utility which

minimize the impact of the application on the Linux file system cache

Use case: backup processes that should not affect the current state of the cache.

• using dd there is direct input / output for a bysab according to this question
• dd nocache, info coreutils 'dd invocation'