Is there a read only cache for rclone mount?

In rclone mount is there a way to set read only cache ?
I am using rclone mount to mount a remote and use macrium backup to backup to it. Macrium backup reads previous files (around 10 gb each) to determine changed files. Is there a way to cache the reads but not cache the writes ? I want to write directly to remote.

Not currently no. Surely you'd want the writes to be cached as they'll be the reads for the next run of Macrium won't they?

Only the beginning of file needs to be cached. What happens if I allocate 10GB cache and write 20 GB of data ?

The caches uses sparse files so it only caches what it needs.

If you have a 20GB file, it will cache as much as you can read. Once the polling for the cache happens and you have more than 10GB, it cleans what it can.

Docs are here:

rclone mount

and here for the size part:

rclone mount

It depends exactly, but rclone will try to keep the cache below 10GB. It will be able to do this provided there isn't more than 10GB of un-uploaded data. If your upload is one 20GB file then it will fail, but if it is lots of smaller files it will likely suceed depending on exactly how fast your internet connection is, etc.

Why does it not switch to writing without cache mode once the cache is filled ? Why does it fail ?

It fails because you fill a disk up and filled disks tend to break things :slight_smile:

The disk still has free space. Just the cache is limited to 10gb right ?

Correct. As long as the disk doesn’t fill up, you’d be fine. I use a SSD for cache and I leave a little buffer space for my two mounts just in case and never have had any issues.

Okay, so if the disk cache fills up but disk doesn't fill up it will be fine ?

Yes, if you read this part, it's documented here as that's why I shared the link as it explains it: