Diff backup is not really a Diff one, as it takes the Diff always from the full



I installed today and its really simple to use, very nice, BUT there is - for my understanding - a logic mistake within the Diff backups.

A Diff backup usually means:
Full backup 12:00 - 100 MB
Diff 12:15 - 10 MB (the increase from the last 15 Mins)
Diff 12:30 - 3 MB (the increase from the last full, including the last diff).
Diff 12:45 - 20 MB (the full, all diffs and the change now)

But with SQLBAckupandFTP
Full 100MB
12:15 10MB
12:30 - 13 MB (full + all)
12:45 - 33 MB (full +all)

I want to keep backups for few days, but with this method and just few GB DB, the space need is enormous.

I backup on: hd, cloud network AND ftp - how can i handle this massive space - as diff. backup is working in this case a bit…different? :smiley:


Hi Tom14,

A differential backup is created similarly to a full backup, but with one important difference – the differential backup only contains the data that has changed since the last full backup (the active portion of the transaction log). Differential backups are cumulative not incremental. This means that a differential backup contains all changes made since the last full backup, in spite of the fact that they have already been included in previous differential backups. https://sqlbak.com/academy/differential-backup/

According to your scenario, perhaps, you meant transaction log backup. A transaction log backup contains all transaction log records that have been made between the last transaction log backup or the first full backup and the last log record that is created upon completion of the backup process. https://sqlbak.com/academy/transaction-log-backup/

It seems you need to perform:
Full backup - 12:00
Transaction Log - backup 12:15
Transaction Log - backup 12:30
Transaction Log - backup 12:45