Differential Backups, what happens to the previous backups?

[saas1980]

Hi, I'm running Windows 10 using 'Cobian backup'

To date, I have always relied on full backups on a weekly basis and before my external drive approaches its full capacity, I delete most of the previous backups to keep it running smooth.

Now I want to switch to differential backups (eyeing on incremental too). I wanted to know whether the differential option will allow me to view the files which were backed up previously. As I understand, differential backups revert back to the initial full back up on day 1 to produce the latest backup with all changes since. Assuming on day 6 the new backup of all changed files since day 1 is produced, what happens to files and folders of day 2, 3, 4 and 5? Assuming these are not overwritten or deleyed, would these previous files and folders be accessible?

The reason why I ask is assuming today I accidentally deleted a file without realising and after the new backup is produced I want the option to view the previous days backup to retrieve the file. Is this possible?

 

[colelouiscloud]

Differential backups only back up what was changed or added since the last backup. If you already have a full backup then a differential backup will only back up the changes made since the last backup. Don't quote me on that, but still...

 

[gardenman]

I just did a quick test with Cobian backup. Using the Differential option, I told it to backup a single program and the only changes that I made to the program was the INI file (settings file for the program) each time I ran the backup. After the initial backup, each additional backup only included the INI file as expected. See the file sizes in the picture below. I told the program to keep 3 differential copies (you can choose the number of differential backups to keep under Task Properties / Dynamics). I was able to access the previous backups by simply opening the 7zip file. All backups are saved up the number of backups that you decide to keep with that setting.

So if you choose to keep 3 differential backups, the original backup is kept and on the 5th day, the 1st differential backup is deleted. <-- That's complicated. Let's look at it like this. Assuming daily backups:

Day 1:
Original Backup

Day 2:
Original Backup
Diff 1

Day 3:
Original Backup
Diff 1
Diff 2

Day 4:
Original Backup
Diff 1
Diff 2
Diff 3

Day 5:
Original Backup
Diff 2
Diff 3
Diff 4

Diff 1 is automatically deleted on Day 5 because I only wanted to keep 3 differential backups. I can still access the Diff 2 backup if I want to access those files.

So yes, the previous differential backups are available, but only up to a certain point (the number of differential backups you choose to keep). You can probably leave the number of differential backups to keep set to 0 for an unlimited number of differential backups.

 

[saas1980]

I just did a quick test with Cobian backup. Using the Differential option, I told it to backup a single program and the only changes that I made to the program was the INI file (settings file for the program) each time I ran the backup. After the initial backup, each additional backup only included the INI file as expected. See the file sizes in the picture below. I told the program to keep 3 differential copies (you can choose the number of differential backups to keep under Task Properties / Dynamics). I was able to access the previous backups by simply opening the 7zip file. All backups are saved up the number of backups that you decide to keep with that setting.

So if you choose to keep 3 differential backups, the original backup is kept and on the 5th day, the 1st differential backup is deleted. <-- That's complicated. Let's look at it like this. Assuming daily backups:

Day 1:
Original Backup

Day 2:
Original Backup
Diff 1

Day 3:
Original Backup
Diff 1
Diff 2

Day 4:
Original Backup
Diff 1
Diff 2
Diff 3

Day 5:
Original Backup
Diff 2
Diff 3
Diff 4

Diff 1 is automatically deleted on Day 5 because I only wanted to keep 3 differential backups. I can still access the Diff 2 backup if I want to access those files.

So yes, the previous differential backups are available, but only up to a certain point (the number of differential backups you choose to keep). You can probably leave the number of differential backups to keep set to 0 for an unlimited number of differential backups.

Gardenman, you are an absolute legend!!

Thanks for taking the time to test it out and the 'differential copies to keep' option is EXACTLY what I needed! Kinda odd, i can't find that option for selecting 'best solution'.

If you are using cobian too, in the backup reports I get a number of error logs in red font. I always ignore these as the location directories are more system related opposed to my personal/work files and folders. Should I be concerned or is this expected?

 

[gardenman]

I'm not using Cobian yet... but I have had it downloaded (along with another program) and I just haven't decided on which one I'm going to use yet. I have installed it a few times into my test system just to look at things and test it out. I kinda like it, I might choose it over the other one.

A question for you, when you say you are doing a "full backup", do you mean ALL files on the system? Including the Windows folder? If so, you are using Cobian incorrectly. Let me explain.

There are 2 types of backups, a file backup (which Cobian is excellent for), and a system backup (which Cobian cannot do).
1. A file backup is for personal files, such as documents, pictures, videos, music, etc.
2. A system backup includes Windows and everything on the computer.
While you can attempt to backup Windows and everything with Cobian, unfortunately it will not be able to do a full restore because Cobian is a a file backup program only.

If you are using it to backup Windows and other folders, then you will likely receive errors about not having permission to access certain folders, hence the red errors. Cobian wasn't designed for that.

Read the first paragraph on this page: http://pgoh13.com/cobian_backup.php

So you have a few choices. Either dial back the files you are backing up with Cobian and use it to backup only personal files, or, get a different backup program that is capable of doing a system backup. I can't exactly recommend one. I use Paragon backup and recovery 14 free for my system backups (some people don't like it). Version 16 doesn't work for me.

Here are some other backup programs: https://www.lifewire.com/free-backup-software-tools-2617964
I know these 3 are also capable of doing a system backup:
AOMEI Backupper Standard
EaseUS Todo Backup
Macrium Reflect

 

[saas1980]

I only back up 'user' files and folders and cloud storage files which are relocated to my second drive. The error files are usually from the AppData folder and some other files from hidden folders, besides the outlook pst/ost which backups fine, I don't think I need the rest of it. Just not sure whether the errors in cobian logs are common for these types of sys/app files.

So to throw in another question: Incremental backups, how does this back up deal with previous day backups? Overwritten?

 

[gardenman]

These are common errors and the errors that I am getting on the AppData folder are because the files are opened in another process and Cobian is unable to copy them to create the backup. [Screen Shot]

ERR 2017-09-26 18:22 An error occurred while compressing the file "C:\Users\GardenMan\AppData\Local\TileDataLayer\Database\EDB.log": The process cannot access the file because it is being used by another process
ERR 2017-09-26 18:22 An error occurred while compressing the file "C:\Users\GardenMan\AppData\Local\TileDataLayer\Database\EDB.log": The handle is invalid

Cobian came with something called Volume Shadow Copy which would have allowed this, but I think it quit working when the Windows Creators update was released, maybe even before that. The reason I know this is the same system was also used on Paragon Backup and it quit working, however, it has an alternative so I am able to continue using it. Just keep in mind that those files are not backed up.

Incremental works differently. It only backs up the files that have changed since the last incremental backup. This makes the incremental backups smaller than differential, which backs up all changes since the original full backup. So it doesn't delete the previous incremental backups because it relies upon them to determine which files need to be backed up or not. (I'm learning all of this as I go too). With Cobian, you can force a full backup to happen every X (configurable number) of backups. Here's an example that I tested out:

Setting: Make full backup once every 3 backups
Setting: Incremental
Setting: Full copies to keep: 1

Day1:
Full

Day 2:
Full #1
Incremental #1

Day 3:
Full #1
Incremental #1
Incremental #2

Day 4:
Full #1
Incremental #1
Incremental #2
Incremental #3

Day 5:
Full #2

So on day 5, a new full backup is automatically created. Cobian deletes the older backups. However, you don't have to create a full backup every X days. You can choose to ignore that setting and it will simply keep backing up only new changes since the last incremental backup.

 

[USAFRet]

What a Differential does depends completely on what the software is.
Macrium does it differently than Cobian does it differently than Acronis.

Macrium (my personal fave), automatically deletes old Differential or Incremental on whatever schedule you set up.
Differential is everything that has changed since the last Full backup.
Incremental is everything that has changed since the last Full or Incremental.

And Macrium gives you the functionality to open a Full, Diff, or Inc image, just like any other folder. The Macrium clien gives it a drive letter, and opens it in Explorer.