Question about disk cache

My question is not only related to URBACKUP, but the way any backup software may interfere with disk caches.

I have a server with several magnetic HDDs and one small SSD using bcache to improve its performance. As I understand, bcache “caches” the most read blocks of the HD, and I am wondering if urbackup (or any backup tool in this case), may interfere with this. Basically my questions are these: as all the data from the storage pool is read periodically, how bcache detects what is the most used data to keep in the cache? Do you know if there is a way to tell URBACKUP to bypass cache, or bcache to ignore the reads from the backup client (not count them in the statistics used to select what needs to cached up)?
I know this may be a question better suit for bcache forum, but maybe any of you guys can tell me what I’m missing, or if my assumption is correct, and there is no real benefit of using bcache in a machine that is being backed up regularly.


Bcache has a configuration option that makes sequential reads bypass the cache. That one is on per default and if that is on it shouldn’t put the data read for backups into cache.

Thanks for your answer. I have one more question. Is this true even I’m backing up files and not making an image?