The only bad experience you will have is the saturation of all your CPU cores/threads may affect your System's response. This depends on CPU in use. The compression method is very safe, no issues.
To be honest. Who in their right mind would do very intensive stuff with their system while backing up the C-drive? If a backup takes a complete backup of the C-drive with a duration of 5 minutes nobody want take the risk that files that are backup at the start and other files at the end differs when both files have an important relation with each other.
It's always wise to have no heavy programs running while making an backup. I don't think the Hasleo isn't that CPU heavy. In the end it alle depends on the user using compression. I backup my C-drive with a low compression rate. The only thing that is heavy is the load on the disk. If you set your compression rate to high then yes; you will give your CPU an additional heavy task: beside backing up your data it also has to compress it in order to reduce the backup file size. It will take also more time to backup if you don't have a fast CPU. The same will be restoring an backup. It will take more time to restore with high then it would with low. So you must take your system specs into account and alter settings that will give you a good and fast backup. Those backups are a real lifesaver when things go wrong. Yes I also learned my lessons the hard way! Lost everything with no backup......Fxxx....
I will you give an example what I have and do while I am backup my C-drive. (having a fast system does help)
- No programs are running while I made the backup. Except a couple standard programs (incl. 3rd-party) that started when Windows started. (Win11, 25H2)
- I have a good CPU; Intel i7-12700K; 12-core (8 Performance-cores, 4 Efficient-cores), 20 threads. A 12th Gen CPU.
- C-drive; a 250GB NVMe Samsung 960 EVO. Not a very fast drive. Filled (Current) with 87Gb of Windows data. (cleaned junk files and cleaned the registry first)
- Backup drive a 2TB NVMe Samsung 990 Pro. A very fast drive.
- A recent complete backup file of the C-drive with a low compression rate is 34Gb stored on my backup drive.
- Time it took to make a full backup: 1 Minute.
- Time to do a full verify of that backup: 36 seconds.
What I love at the Hasleo backup software; you can do it online (Disk is accessible (off course) and (worse) Windows is running) with no repercussions.
There is a better and saver way though. This online backup is unusual: backing up while Windows is up and running (Some process or services can lock files and granting no access (for reading) to them or worse altering their content!) A better way is to prepare a WinPE image, boot from it and make the backup. (offline backup) Like it is the case when Hasleo restores a backup. Unfortunately I see no option inside the Hasleo software for making an offline backup.
I will investigate this further and asking Hasleo for an answer. (If you want a 1000% save backup this is the way to do it; offline backup)