Error download_chunk

Support
#1

Hi, I have a backup job which has been active for a couple of years. The backups appear to complete ok, however I’ve noticed recently that my regular check and prune commands are failing with the “ERROR DOWNLOAD_CHUNK” message.
I’m unsure whether this means more recent backups aren’t actually going to be restorable. I’m not especially worried about finding out what caused this to happen, I’d just like it to stop happening so I can be sure backups going forward will actually work.
I’ve read other posts suggesting to change the backupid, but I’ve also read that Duplicacy might still assume chunks exist which actually might not. The result from the most recent -check I ran via the web interface is below.

Thanks,
David

Running check command from /Users/davidspink/.duplicacy-web/repositories/localhost/all
Options: [-log check -storage JMHM -a -a -tabular]
2021-02-04 23:08:21.086 INFO STORAGE_SET Storage set to b2://BACKUP-JMHM
2021-02-04 23:08:22.027 INFO BACKBLAZE_URL download URL is: https://f001.backblazeb2.com
2021-02-04 23:08:23.800 INFO SNAPSHOT_CHECK Listing all chunks
2021-02-04 23:32:14.177 INFO SNAPSHOT_CHECK 3 snapshots and 6259 revisions
2021-02-04 23:32:14.182 INFO SNAPSHOT_CHECK Total chunk size is 1135G in 302153 chunks
2021-02-04 23:32:23.830 INFO SNAPSHOT_CHECK All chunks referenced by snapshot JMHM1-jmhadmin-14-OldJMH at revision 1 exist
2021-02-04 23:32:31.224 INFO SNAPSHOT_CHECK All chunks referenced by snapshot JMHM1-jmhadmin-14-OldJMH at revision 5 exist
2021-02-04 23:32:36.927 INFO SNAPSHOT_CHECK All chunks referenced by snapshot JMHM1-jmhadmin-14-OldJMH at revision 9 exist
2021-02-04 23:32:39.976 INFO SNAPSHOT_CHECK All chunks referenced by snapshot JMHM1-jmhadmin-14-OldJMH at revision 13 exist
2021-02-04 23:32:47.451 INFO SNAPSHOT_CHECK All chunks referenced by snapshot JMHM1-jmhadmin-14-OldJMH at revision 17 exist
2021-02-04 23:32:55.004 INFO SNAPSHOT_CHECK All chunks referenced by snapshot JMHM1-jmhadmin-14-OldJMH at revision 21 exist
2021-02-04 23:33:05.212 INFO SNAPSHOT_CHECK All chunks referenced by snapshot JMHM1-jmhadmin-14-OldJMH at revision 25 exist
2021-02-04 23:33:08.908 INFO SNAPSHOT_CHECK All chunks referenced by snapshot JMHM1-jmhadmin-14-OldJMH at revision 29 exist
2021-02-04 23:33:09.437 INFO SNAPSHOT_CHECK All chunks referenced by snapshot JMHM1-jmhadmin-14-OldJMH at revision 32 exist
2021-02-04 23:33:10.663 INFO SNAPSHOT_CHECK All chunks referenced by snapshot JMHM1-jmhadmin-ServerFolders at revision 789 exist
2021-02-04 23:33:10.840 INFO SNAPSHOT_CHECK All chunks referenced by snapshot JMHM1-jmhadmin-ServerFolders at revision 830 exist
2021-02-04 23:33:10.986 INFO SNAPSHOT_CHECK All chunks referenced by snapshot JMHM1-jmhadmin-ServerFolders at revision 861 exist
2021-02-04 23:33:11.689 INFO SNAPSHOT_CHECK All chunks referenced by snapshot JMHM1-jmhadmin-ServerFolders at revision 882 exist
2021-02-04 23:33:12.260 INFO SNAPSHOT_CHECK All chunks referenced by snapshot JMHM1-jmhadmin-ServerFolders at revision 909 exist
2021-02-04 23:33:12.826 INFO SNAPSHOT_CHECK All chunks referenced by snapshot JMHM1-jmhadmin-ServerFolders at revision 935 exist
2021-02-04 23:33:13.422 INFO SNAPSHOT_CHECK All chunks referenced by snapshot JMHM1-jmhadmin-ServerFolders at revision 961 exist
2021-02-04 23:33:13.996 INFO SNAPSHOT_CHECK All chunks referenced by snapshot JMHM1-jmhadmin-ServerFolders at revision 989 exist
2021-02-04 23:33:14.895 ERROR DOWNLOAD_CHUNK Chunk 4b454a5d809209aa66c426eedff8694e4549467cf19c2fa0abba031719fa1f1c can’t be found
Chunk 4b454a5d809209aa66c426eedff8694e4549467cf19c2fa0abba031719fa1f1c can’t be found

#2

Looking at the setup I also just realised I have two different backups with the ID “JMHM1-jmhadmin-ServerFolders”, should they have different IDs?
David

#3

Duplicacy assumes that all chunks referenced by the last revision with the same backup id exist, so if you change to a new backup id it will try to re-upload all chunks.

Yes, if they are from different repositories they should have different IDs.

#4

Great, thanks for the assistance. I’ll do both these things. David

#5

I’ve changed my backup IDs so each of the, now, 3 backups is using a different name. However whenever I run a Check it still stops after complaining about a missing chunk. The missing chunk appears to relate to the old backup ID which is no longer used for backup.

What can I do now to clear this missing chunk error?

David

Running check command from D:/Duplicacy Cache/cache/localhost/all
Options: [-log check -storage JMHM -a -tabular]
2021-02-17 21:51:53.488 INFO STORAGE_SET Storage set to b2://BACKUP-JMHM
2021-02-17 21:51:54.714 INFO BACKBLAZE_URL download URL is: https://f001.backblazeb2.com
2021-02-17 21:51:57.086 INFO SNAPSHOT_CHECK Listing all chunks
2021-02-17 22:16:18.069 INFO SNAPSHOT_CHECK 5 snapshots and 6692 revisions
2021-02-17 22:16:18.107 INFO SNAPSHOT_CHECK Total chunk size is 1138G in 303487 chunks
2021-02-17 22:16:19.256 INFO SNAPSHOT_CHECK All chunks referenced by snapshot JMHM1-jmhadmin-ServerFolders at revision 789 exist
2021-02-17 22:16:19.681 INFO SNAPSHOT_CHECK All chunks referenced by snapshot JMHM1-jmhadmin-ServerFolders at revision 830 exist
2021-02-17 22:16:20.074 INFO SNAPSHOT_CHECK All chunks referenced by snapshot JMHM1-jmhadmin-ServerFolders at revision 861 exist
2021-02-17 22:16:21.339 INFO SNAPSHOT_CHECK All chunks referenced by snapshot JMHM1-jmhadmin-ServerFolders at revision 882 exist
2021-02-17 22:16:21.948 INFO SNAPSHOT_CHECK All chunks referenced by snapshot JMHM1-jmhadmin-ServerFolders at revision 909 exist
2021-02-17 22:16:22.439 INFO SNAPSHOT_CHECK All chunks referenced by snapshot JMHM1-jmhadmin-ServerFolders at revision 935 exist
2021-02-17 22:16:22.999 INFO SNAPSHOT_CHECK All chunks referenced by snapshot JMHM1-jmhadmin-ServerFolders at revision 961 exist
2021-02-17 22:16:23.499 INFO SNAPSHOT_CHECK All chunks referenced by snapshot JMHM1-jmhadmin-ServerFolders at revision 989 exist
2021-02-17 22:16:25.083 ERROR DOWNLOAD_CHUNK Chunk 4b454a5d809209aa66c426eedff8694e4549467cf19c2fa0abba031719fa1f1c can’t be found
Chunk 4b454a5d809209aa66c426eedff8694e4549467cf19c2fa0abba031719fa1f1c can’t be found

#6

You can follow this guide to fix the missing chunk. The first thing you should try is to check if it is caused by a stale cache, as explained in the guide.

#7

If you no longer use that backup ID, then best to delete the relevant folder (\snapshot\<backup_id> on the storage, and delete the stale cache. Do the check then finally run a prune -exhaustive to clean it up.

#8

Thank you, I’ve done as suggested deleting both from the storage and the local cache, etc, and now the check is completed ok.