borg2: Files cache not used, backups quite slow

[ThomasWaldmann]

When i run a backup with --debug i get this message
Reading files cache ... The files cache can't be read. [[Errno 2] No such file or directory: '/home/dietmar/.cache/borg/23581be32c02fcf0fec04495a7b3fbe9051ae082a0622274cbd1235d707ca02c/files.7e6fd736306eb290']
and it does not look for the existing files cache. The hash above is the name this run is going to write. After the run
dietmar@eselspinguin-zfs:~/borgbackup/log/borg-200b13$ ls -al ~/.cache/borg/23581be32c02fcf0fec04495a7b3fbe9051ae082a0622274cbd1235d707ca02c/*7e6fd736306eb290* -rw------- 1 dietmar dietmar 23381424 6. Nov 05:59 /home/dietmar/.cache/borg/23581be32c02fcf0fec04495a7b3fbe9051ae082a0622274cbd1235d707ca02c/files.7e6fd736306eb290

At the end the statistics show all files as new and borg did a benchmark of my notebook SSD. Unfortunately my fileserver has a RAID of spinning disks which really need the file cache

Duration: 31 minutes 29.425 seconds Number of files: 155374 Original size: 494.39 GB Deduplicated size: 240.03 MB Time spent in hashing: 14 minutes 37.134 seconds Time spent in chunking: 15 minutes 29.983 seconds Added files: 155374 Unchanged files: 0 Modified files: 0 Error files: 0

Originally posted by @dietmargoldbeck in #8509 (comment)

[ThomasWaldmann]

This is because borg2 now automatically derives the files cache suffix from the archive (series) name.

Guess the upgrade notes should mention to either:

• switch to "archive series" way of naming archives (always the same short name, no timestamp in the name, no user/host in the name), or to
• use BORG_FILES_CACHE_SUFFIX to manually manage the suffix. either always use the same suffix or set a unique one per source file data set.