I have a second hard drive (which is not system drive) inside the system unit which contains data which needs to be backed up regularly. I have never used backup software and need to find a program which can compare the files on the drive inside the system unit with the files on the external backup hard drive to determine what files in the first drive are not found on the backup drive, and if not, copy them to the backup hard drive when it is connected to the computer twice a month. The program should also automatically delete from the backup drive files which are no longer stored on the drive inside the system unit.
What software can perform the above actions?

Hmm. So, if you (or a drive problem) accidentally delete a file on the system drive, the backup program will delete the back-up copy automatically? Not my idea of a back-up.

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Yes, I need backup software which has the function to synchronize the source and the backup drives so that the backup drive is the exact copy of the source drive.
Such synchronization will also save much time, because the program will not have to delete all the data on the backup drive and write onto it all of the data from the source drive each time when a backup is made, but only those files on the source drive which are not found on the backup drive.

Robocopy with the /mir option, do a search for it, lots of examples available.

@LarrySabo, not sure what the OP is using for an external backup, but if it is a Synology NAS with snapshots, you don't need to worry about not being able to recover deleted files

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Thank you. I am using an ordinary hard drive as an external backup device. I need the two drives to be synchronized. Therefore, some synchronization software can be used to copy data onto the external drive.

It may be a lot better if you say which backup software you have tried, and why the ones that did not meet expectations fail the test.

also, a quick google for "backup software free" shows:

Best free backup software - at a glance:

EaseUS Todo Backup Free.
Cobian Backup.
Paragon Backup & Recovery.
FBackup.
Google Backup and Sync.

https://www.pcworld.com/article/3235812/the-best-free-backup-software-and-services.html has some reviews of some of these at the bottom. It might pay to read them and at least get more familiar with backing up, backup options, pro's and con's etc.

If you have never used backup software before, then it may be that the idea you have for backing up is flawed. no fault of yours, but sometimes in I.T. the questiion you asked is not really the right one.

for example, some of the ways your current idea is flawed:

- your working files and your backups are in the same place. A lightning strike, fire, dog/cat accident at the PC, fire sprinkler damage, theft could all result in both working and backups going bye-bye.

- A ransomeware would likely encrypt working and backup files

- a problem with working files will likely get copied to your backups.

All that aside, a search for software/tutorials using the keyword "incremental" is what will steer you right.

lastly, consider online backup. once the initial big backup is done, subsequent ones are not that big, and it is totally off-premises, safer and the backup companies think of things you dont!

PS. a windows forum may be a better place to ask.

Thank you. I have not yet tried any synchronization software and do not need some complex methods of doing backups. I am going to try DirSync, since it is said to be able to synchronize two directories, making both folders identical in contents.

Quoting Vlad5: The program should also automatically delete from the backup drive files which are no longer stored on the drive inside the system unit.



I'm with LarrySabo, your backup drive should not allow automatic deletion of any of its folders or folders just because the source has any one or more folders or files. If you or anyone accidentally deleted a critical or important folder (with files in it) or file(s), and do not immediately data recover said deletions on the source drive, and if the backup drive same folder(s) and/or file(s) are auto-deleted -- you may very well have problems getting those things back. Now, what you can do is set up a NAS which will do what you want during the day, and, have an external USB hard-drive with backup/restore software that will do weekly or bi-monthly images.
(If you decide on the regular images-backup routine, the NAS could function as a file-server to your numerous employees if you have a business.

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"Take care of thy backups and thy restores shall take care of thee." Ben Franklin revisited

I think that simply synchronizing the source drive with a backup drive is sufficient for me. But in the case of businesses which need to maintain data security, a more complex way of backup up data may be needed.

"...your backup drive should not allow automatic deletion of any of its folders or folders just because the source drive has one or more folders or files deleted.,," me, in an earlier post, with a correction inserted.

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"Take care of thy backups and thy restores shall take care of thee." Ben Franklin revisited