AFAIK all disk reads on linux get into the page cache.

Is there a way to prevent reads (done by a backup process) to get in to the page cache?

Imagine:

• A server runs fine, since most operations don't need to touch the disk, since enough memory is available.
• Now the backup process starts and does a lot of reading. The read bytes get into the memory (page cache) although nobody wants to read the same bytes again in the next hours.
• The backup data fills up the memory and more important pages from the cache get dropped.
• Server performance gets worse since more operations need to touch the disk, because the relevant pages were dropped from the cache.

My preferred solution:

• Tell linux that the reads done by the backup process don't need to be stored in the page cache.