That's a good question really, I would suggest that backup software should be 100% reliable or as close as makes no difference. Having used FBackup a while ago and not really being a believer in "free" software I purchased Backup4All to ensure I get a reliable backup of my work machine every night.
After a while I started getting reports that my backup completed with thousands of warnings. On investigating the log it showed that these files could not be found.
Clearly sifting though a log of this size wastes a lot of time so I ignored it a couple of times. You get the impression from the software that the backup is somehow "stuck" and is still running which is quite confusing. After few of these reports I decided to contact Softland support. After sending off logs and answering various questions they suggested a remote support session on 06/11.
Following this they assured me that the backup we were inspecting was complete and that I should not be concerned however there was no explanation about why I periodically get these reports which after all, indicate something went wrong with the backup. I kept track of potentially failed backups following the support call, they seem to happen every 6 days (05/11, 12/11, 18/11, 24/11, 30/11, 06/12, 12/12, 18/12, 24/12) which is quite odd. Softland state "If an external factor (maybe antivirus) is blocking/deleting the extracted files in temp and Backup4all is not able to find them, the problem is with Backup4all?", well yes it is! The workstation has no additional virus products beyond Windows Defender and Backup4All should easily cope with a very clean and standard Windows installation.
So, according to Softland I should ignore reports that the backup has not completed correctly and they are unable to advise why their software is having a problem. All this is on a brand new Dell workstation with massive resources. I was both speechless and quite angry at their attitude so started digging through their website.
I quote: "Our core values differentiate us from the competition. Reliability and usability ... attention to detail". Sorry guys, I would beg to differ and am now on the lookout for a more reliable package.
My advice for what it's worth is don't buy Backup4All, seek out something more reliable, after all when disaster strikes and you need that backup you want to feel confident it's going to be there for you.