The docs are not clear. If I do restic check --read-data 100 and my repository is S3, does restic download and check my repo using my local hard disk or local RAM? Meaning, is I/O being wasted downloading and checking files or is it all being done with RAM?
I don’t know the answer, but I expect it could be found out easily enough by running a restic check –read-data and then doing iotop -p <pid of restic> and watching the output.
IIRC, check –read-data reads the data blobs directly from the backend and checks them in-memory.
(Note that tree packs are read from the backend and stored in the cache dir - unless –no-cache is used - if they are not yet present there. But this is the wanted behavior 
)