Hi at all,

following general conditions are given:

- 12 node Proxmox-Cluster (48 x Intel(R) Xeon(R) CPU E5-2690 v3 / 256
GB RAM)
- 96 Osd Ceph-Pool -> 6x HDD / TOSHIBA_MG07ACA14TE + 2x SSD /
SAMSUNG_MZILT7T6HALA_007 (Ceph-DB) per node
- 10 GBit Network
- 10 PBS VMs running
- 1 PBS VM (55 GB RAM, 16 CPUs, 35 TB Backup-Datastore XFS)

Last mentioned PBS VM ist connected with another Proxmox-Cluster (9
nodes 24 x Intel(R) Xeon(R) CPU X5670, 142 GB RAM, 56 SSD OSDs, 30 VMs
running) as Backup-Storage for VMs. 1 VM running on this cluster (32 GB
RAM, 16 CPUs, 12 TB HDD (virtio, discard, iothread), OpenSuse Leap
15.4) is mailserver. 12 TB HDD has one directory "MAIL" with 23000
subdirectories (1 subdir per user), 10 TB are in use. PBS-client per
CLI is working without any problems - for example: mapping PBS-snapshot
and listing subdirs in MAIL-directory.
Listening / viewing subdirectories of MAIL-dir per Web-GUI (VM ->
Backup -> File Restore -> click "+" of MAIL-dir) is not working. After
waiting for about 4-5 minutes error code "list not finished in time
(503)" appears. Logfiles (/var/log/proxmox-backup/file-restore/qemu.log
+ journalctl) do not show anything "unnormal" or error related.

What exactly is the root cause of this behaviour and how to solve this?
Any hint / thought is welcome / helpful....

best regards
Th. Naumann