Backup or reindex job fails in Comet Backup: zero-byte pack file

Symptoms

Backup or reindex job fails with a message similar to this line:

CONFIG_TEXT: Couldn't index contents of pack <data/xxxxxxxx>: Retried 1 times over 0:00: zero-byte pack file

Cause

Zero-byte files are usually a symptom of disk or RAID array failure and/or file system corruption, and a subsequent fsck or chkdsk. 

Resolution

1. Use a new storage location while investigating this data corruption. With that, backups will not be interrupted, but they will be stored in a different storage.
2. To delete zero-byte files, cd to the storage directory and run one of the following commands:

   • Linux: 

     # find . -type f -size 0 -print -delete

   • Windows:

     C:\> Get-ChildItem -Recurse -File | ForEach-Object {
       if ($_.Length -eq 0) {
         Write-Output "Deleting zero-byte file: $($_.FullName)";
         Remove-Item $_.FullName
     }

3. Re-index the Storage Vault after deleting the files, then run a retention pass to see which snapshots are not restorable.