To design a sound and useful backup strategy we should know about the different types of backup options available with the backup software. I have written here about various types of backup options available in NovaBackup. I am using the same scenarios during product demonstration to the customers.
Below is the list of types of backup supported by NovaBackup:
Full backup
The full backup backs up all files from the source and resets the archive attribute of each file. Let us have an example to understand this:
I have created a folder named ‘Source’ and 6 files (two text files, two document files and two excel worksheets). Immediately after doing this I checked for archive file attribute for each file and found that this attribute is set for all files. The archive file attribute indicates that whether the file has been modified or not since last full/incremental backup. To check file attributes launch Command Prompt, change folder to Source (cd source) and then issue attrib command (shown in left part of the Figure 1). Attrib command will show all attributes for each file existing in the current working folder.
Let us create a full backup job using NovaBackup Pro/Server/Business Essential having folder ‘Source’ as source to be backed up, Backup Mode as Full and Write Mode as Append to Media. After executing the full backup job, I again checked for archive file attribute, and found that they have been reset (refer right part of the Figure 1).
Figure 1 :: Archive File Attribute after Full Backup
I modified two files (1.txt and 2.docx) and then check for the status of archive attribute (shown in left portion of the Figure 2). Again ran the same full backup job and then checked the status again and found archive attribute of each file were reset.
Figure 2 :: Archive File Attribute after Full Backup
Based on the above discussion we conclude that Full backup backs up each file irrespective of whether it was modified or not since last backup from the source folders/partitions selected and after backing up each archive attribute is reset.
Full backup forms the base for every backup strategy employed so far in the backup world. The base formed by full backup is frequently updated by taking more full backups. The frequency of full backup is lower than incremental/differential backup e.g. Weekly (weekend), bi-weekly or monthly.
Incremental backup
Incremental backup backs up each file from the source modified after last Full or incremental backup whichever is earlier and after backing up files resets the archive attribute. What incremental backup does is it select files with archive attribute set, backs it up and then reset archive attribute.
Let us have an example to understand incremental backup. Moving ahead from the previous example let us assume after Full/Incremental backup users have modified 1.docx, 2.xlsx and added/created two new file incr1.docx and incr1.xlsx. Checking archive attribute before executing incremental backup job shows archive file attribute set for files 1.docx, 2.xlsx, incr1.docx and incr1.xlsx (See left portion of Figure 3).
Now I created an incremental backup job using NovaBackup Pro/Server/Business Essential and manually executed it and then again checked for the status of archive attribute and I found they were reset as shown in right portion of the Figure 3.
Figure 3 :: Archive File Attribute after Incremental backup
In short incremental backup job backs up only the files with archive attribute set from the source and then resets the archive attribute of those files. Thus the backup time is reduced. Incremental backup is most commonly used in combination with Full backup to form the backup strategy.
Each incremental backs up only the files/folders modified and created after last full or incremental backup due to this the backup time is reduced. However this forces us to maintain all the incremental backup sets taken after the base created by full backup.
To restore data from the backups we need to follow below steps:
- First restore latest full backup (base backup)
- Then restore each incremental set backed up after latest full backup starting from older to newer ones one by one.
Later in a separate post on Restore process using NovaBackup Professional / Server / Business Essential we will see that how Time slider technology helps us to restore point in time data without knowing on which device or backup set the data is in.
Differential backup
Differential backup backs up each file from the source modified/created after last Full or incremental backup and after backing up files it keeps the archive attribute intact.
After taking full backup I modified 1.txt, 1.docx, 1.xlsx and also created a new file differential.txt. The status of archive attribute is as per left portion in Figure 4. I took differential backup of the folder ‘source’ and then checked for the status of archive attribute (right portion of Figure 4). The archive attributes of files are same as it were before differential backup.
Figure 4 :: Archive File Attribute after differential backup
Differential backup scans for all files in Source whose archive attribute is set, backs them up and keeps the archive attribute untouched. It means that as we move away from last full or incremental backup, the amount of data backed up by differential backup keeps on increasing until we take full/incremental backup again which resets archive attribute of all files in Source. It also means that time taken by differential backup also keeps on increasing as we move away from last full or incremental backup.
Snapshot backup
Snapshot backup is just like a full backup but it does not reset archive attribute after taking the backup. Snapshot backup is used to take manual backup of entire source without disturbing regular backup strategy.
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