Hi 
I’m actually backing up to B2. Today i noticed circa 400 MB of download, but the only interaction i had with B2 was for my daily backup.
So does Duplicacy downloads something when backing up?
Thanks in advance!
Yes.
Duplicacy needs to check which chunk are already stored in the B2 storage so that they won’t be updated again.
It will probably need to list the directories and download some meta information, though I am not sure why it takes 400MB over multiple backups.
Well, a day passed. Now i see 0 egress, and my daily backup has been performed successfully.
So don’t know.
Duplicacy needs to access the metadata chunks in the previous backup in order to detect which files have been changed. Normally these chunks are stored in the cache, but if the cache is cleared or if the previous backup was done on a different computer, then Duplicacy will download these chunks again from the storage.
Another possibility is that the download traffic may be coming from API responses. Each response may be as large as a few KBytes, and if you have a large number of them, the total amount can become signifiant.
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Thanks.
So the backup is done daily from the NAS itself.
In which occasions the cache is cleared? I never did this manually.
My storage backup is between 800-900 MB. So 381 MB of Metadata chunks are plausible? Also I backup files that rarely Change. Only a few of them is “new” for each backup.
If your backup is only 800-900 MB I don’t know how Duplicacy can generate 400MB of download. Do you still have the backup logs from that day (and any other day with 0 egress for comparison)?
This should be the backup we are talking:
root@DK:/srv/dev-disk-by-label-HC2/AppData/duplicacy/logs# cat backup-20210612-010001.log
Running backup command from /cache/localhost/0 to back up /source/DockerCompose
Options: [-log backup -storage DK_Duplicacy_Backups -threads 10 -stats]
2021-06-12 01:00:02.067 INFO REPOSITORY_SET Repository set to /source/DockerCompose
2021-06-12 01:00:02.168 INFO STORAGE_SET Storage set to XXX
2021-06-12 01:00:04.217 INFO BACKBLAZE_URL download URL is: XXX
2021-06-12 01:00:06.303 INFO BACKUP_START Last backup at revision 83 found
2021-06-12 01:00:06.303 INFO BACKUP_INDEXING Indexing /source/DockerCompose
2021-06-12 01:00:06.303 INFO SNAPSHOT_FILTER Parsing filter file /cache/localhost/0/.duplicacy/filters
2021-06-12 01:00:06.303 INFO SNAPSHOT_FILTER Loaded 0 include/exclude pattern(s)
2021-06-12 01:00:07.991 INFO BACKUP_END Backup for /source/DockerCompose at revision 84 completed
2021-06-12 01:00:07.991 INFO BACKUP_STATS Files: 73 total, 89K bytes; 0 new, 0 bytes
2021-06-12 01:00:07.991 INFO BACKUP_STATS File chunks: 22 total, 242K bytes; 0 new, 0 bytes, 0 bytes uploaded
2021-06-12 01:00:07.992 INFO BACKUP_STATS Metadata chunks: 3 total, 20K bytes; 0 new, 0 bytes, 0 bytes uploaded
2021-06-12 01:00:07.992 INFO BACKUP_STATS All chunks: 25 total, 263K bytes; 0 new, 0 bytes, 0 bytes uploaded
2021-06-12 01:00:07.992 INFO BACKUP_STATS Total running time: 00:00:01
root@DK:/srv/dev-disk-by-label-HC2/AppData/duplicacy/logs# cat backup-20210612-010008.log
Running backup command from /cache/localhost/1 to back up /source/AppData
Options: [-log backup -storage DK_Duplicacy_Backups -threads 10 -stats]
2021-06-12 01:00:08.173 INFO REPOSITORY_SET Repository set to /source/AppData
2021-06-12 01:00:08.173 INFO STORAGE_SET Storage set to XXX
2021-06-12 01:00:09.347 INFO BACKBLAZE_URL download URL is: XXX
2021-06-12 01:00:13.858 INFO BACKUP_START Last backup at revision 78 found
2021-06-12 01:00:13.858 INFO BACKUP_INDEXING Indexing /source/AppData
2021-06-12 01:00:13.859 INFO SNAPSHOT_FILTER Parsing filter file /cache/localhost/1/.duplicacy/filters
2021-06-12 01:00:13.859 INFO SNAPSHOT_FILTER Loaded 0 include/exclude pattern(s)
2021-06-12 01:00:20.362 INFO BACKUP_THREADS Use 10 uploading threads
2021-06-12 01:01:13.057 INFO UPLOAD_FILE Uploaded [...]
2021-06-12 01:01:13.385 INFO BACKUP_END Backup for /source/AppData at revision 79 completed
2021-06-12 01:01:13.386 INFO BACKUP_STATS Files: 31940 total, 1,572M bytes; 131 new, 471,169K bytes
2021-06-12 01:01:13.386 INFO BACKUP_STATS File chunks: 802 total, 2,060M bytes; 15 new, 67,542K bytes, 13,123K bytes uploaded
2021-06-12 01:01:13.386 INFO BACKUP_STATS Metadata chunks: 6 total, 9,921K bytes; 4 new, 5,612K bytes, 1,623K bytes uploaded
2021-06-12 01:01:13.386 INFO BACKUP_STATS All chunks: 808 total, 2,070M bytes; 19 new, 73,155K bytes, 14,746K bytes uploaded
2021-06-12 01:01:13.386 INFO BACKUP_STATS Total running time: 00:01:03
Logs for other days are basically the same if i see them correctly. They are all from the web ui.
Metadata chunks: 6 total, 9,921K bytes; 4 new, 5,612K bytes, 1,623K bytes uploaded
Strange, no idea where the 381 MB are from 
Well, completely forgot that i have also Duplicati backing up the same folders. But the dirs are the same. I will stop Duplicati and see what happens.