It means you do not have any 'live' backups in /var/lib/psa/dumps. I suggest to rename the folder /var/lib/psa/dumps, e.g. to /var/lib/psa/dumps.old and create the new one with the same permissions. Lately /var/lib/psa/dumps.old can be deleted.
Thank you, I renamed it and recreated it:
find /var/lib/psa/dumps -name '*.xml' | wc -l
234
du -h -d0 /var/lib/psa/dumps
11M /var/lib/psa/dumps
time /opt/psa/bin/pleskbackup server -v --configuration --exclude-logs --no-gzip --output-file=/var/lib/psa/dumps
^Accounts [3/38], Domains [6/196], Dumping 'HASH(0x1922630)' in progress
Accounts [4/38], Domains [18/196], Dumping 'HASH(0x1922c60)' in progress
Accounts [5/38], Domains [30/196], Dumping 'HASH(0x19223c0)' in progress
Accounts [7/38], Domains [43/196], Dumping 'HASH(0x191edc0)' in progress
Accounts [13/38], Domains [54/196], Dumping 'HASH(0x191b778)' in progress
Accounts [16/38], Domains [64/196], Dumping 'HASH(0x191bc88)' in progress
Accounts [21/38], Domains [77/196], Dumping 'HASH(0x191e160)' in progress
Accounts [23/38], Domains [89/196], Dumping 'HASH(0x191ea00)' in progress
Accounts [27/38], Domains [102/196], Dumping 'HASH(0x191eb20)' in progress
Accounts [30/38], Domains [114/196], Dumping 'HASH(0x191e898)' in progress
Accounts [30/38], Domains [127/196], Dumping 'HASH(0x191b580)' in progress
Accounts [30/38], Domains [141/196], Dumping 'HASH(0x191b670)' in progress
Accounts [30/38], Domains [154/196], Dumping 'HASH(0x1922750)' in progress
Accounts [30/38], Domains [168/196], Dumping 'HASH(0x191eee0)' in progress
Accounts [35/38], Domains [177/196], Dumping 'HASH(0x1922e58)' in progress
Accounts [35/38], Domains [185/196], Dumping 'HASH(0x191b4d8)' in progress
Accounts [38/38], Domains [196/196]
-------------- Start print backup log hire --------------
<?xml version="1.0" encoding="UTF-8"?>
<execution-result status="warnings" log-location="/opt/psa/PMM/sessions/2018-06-11-120831.981/migration.result">
<message severity="warning" code="msgtext" id="92b0b39a-0e92-46ad-85e4-628e7b14ffe6">
<description>Harness not finished running at /opt/psa/PMM/agents/shared/Storage/ArchiveStorage.pm line 196.
</description>
</message>
</execution-result>
-------------- End print backup log hire --------------
You can view additional information in the log file located in /opt/psa/PMM/sessions/2018-06-11-120831.981 directory. This directory will be removed automatically after 30 days
The backup finished with status 'warnings' and had some problems. Look at log file for detailed information.
real 18m3.935s
user 0m2.500s
sys 0m1.280s
This is shorter than 1 hour. Could it be that it takes so long because that the other directory was more than 3 GB?