How does Windows backup utility work?

I’m using Windows 7. (Actually I’m upgrading to Win10 as I write…)

I backup my laptop religiously every day* to one of two external 1T hard drives. After a week, I switch to the other one, then back and forth weekly. I’ve been doing this for a couple of years. I use the backup utility in the control panel.

My question is how does this utility work? Let’s say the external drive is brand new and empty, and I backup on Monday for the first time. So it copies all my files and apps. When I backup on Tuesday, what is backed up? Does the program look for files and changes from Monday…and what…? Overlay? Make a second copy?

Then after backing up to Drive 1 for a week, I switch to Drive 2. Now there are more new files, some deleted files, changes…what happens? How is it that my backup drives are filling up? (No worries…I’ve got two new ones. I’ve already backed up everything on one of them before I started the Win10 install.)

*I finally got religion on the importance of backing up when Something Bad Happened a few years ago. My most recent backup was, mercifully, only a week old, but it was really inconvenient. I’m a free lancer, and everything is on my laptop.

No one knows? Never mind.

I know squat about Windows backup (and hope to keep it that way), but the way many backup systems work (e.g. - Apple’s Time Machine) is they do incremental backups. That means that the first time a backup is done, everything gets copied. After that, only changed files get copied, but the original is kept, so that you can go back in time and restore a previous version.

What I want to know is this: Is there anything like an actual user’s manual that answers questions like this? I come from an era of computer mainframes, which came with operating systems and piles of system utilities, and these all came from serious manufactures who provided user’s manuals!!!

One of the anachronistic customs that arose with the advent of personal computers, and persists in this day of tablets and smart phones, is the absence of user’s manuals from the manufacturer, or at best, some very sketchy manual. My own cell phone is like that – I’m sure it’s full of stuff that I know little or nothing about, because I’d have to take the offensive and do my own in-depth third-party internet research to learn more.

With systems like Windows or Macs or Linux, one can find whole aisles of books at all the trendy book stores, all from third party sources, for major apps like Word or Excel or SQL Server. But it’s hard to find much more than an on-line help page for the basic utilities.

ETA: P.S. Does anybody from the Silicon Valley area remember the late lamented Computer Literacy book stores in the area?

Thanks for those replies. I figured it was an incremental backup of some sort, but wasn’t sure.

<TL crawls in from the ledge.>

Really, the only way to tell if you’re doing a full or an incremental backup is to check the settings in the backup program. It may be set to do a full backup at the beginning of the week, and then incremental backups for the rest of the week. You can get an idea by seeing how long each backup takes. If it’s like five or ten minutes, it’s almost certainly an incremental backup.

The first full backup onto an empty drive took about six hours. The succeeding ones have taken only a few minutes. But what I was asking in the OP was

So, for a simple example, You, Dewey Finn, live at 123 Main Street. I back up my contacts. Then on Tuesday you move to 789 Elm Street. I back up again. Does the program go in and replace your old address with your new address? Or does it add your new address to the original record? Or does it make a second copy of Dewey Finn’s address record with the new address, leaving the original record intact. So if you move every month for a year, after a year of backing up, will ALL of your previous addresses be in there someplace? Or will each new address replace the previous one? It’s the actual mechanics of *incremental *that I was asking about.
BTW, I loved you in School of Rock. One of my favorite movies.

I’m using Win7 Pro. I’m using Windows backup. It does a full backup when it feels like it, and does incremental backups the rest of the time. It deletes old backups when the disk gets full.

Looking at my backup disk, I’m getting a full backup every month.

AFAIK, WinXP did not have an automatic system of determining if a full or partial backup was reqired. You had to tell it.

Sorry. I don’t know exactly what an incremental backup entails. I assume that it replaces changed files, adds any new ones and deletes any deleted ones, but don’t know for sure.

I don’t understand this, unless it has to do with the brand. My Samsung Galaxy S4 has an official 374-page user manual. No, it didn’t come in the box; I had to download it as a .pdf, but that’s what I would’ve done anyway, because a .pdf document is easier to search.

As for the Windows OS, I kind of agree, in that when you call up help files they aren’t really a user’s manual: It’s more of a how-to guide. I believe OP’s question really is a DOS question. The back-up uses dates and attributes of files to know which haven been changed since the last back up, so it doesn’t have to copy everything all over again each time.

Here’s something else. I have some folders on my computer with gigantic files left over from projects. I’ve done a full backup. I’d like to delete those files from my computer, but I want them to stay in the first backup forever.

Then subsequent daily backups would go from what’s currently on the computer.

What Dewey Finn is describing is what I understand as “syncing,” i.e., making both copies the same.

AIUI, the trick with incremental backups is that the software maintains multiple levels of directories to find current or old versions of files.

Each directory entry on a drive contains not only the stuff you usually see (filename, date, size, …) but also a pointer to where the file is on the disk. If a file has changed (or been created or erased) since the last backup, the backup software makes an updated directory entry on its own drive reflecting the new status. To keep track of all those changes, it maintains what we might as well call a meta-directory, whose entries have saved pointers to all the backed-up versions of files and directories. For unchanged files or directories, the pointers to the old versions remain unchanged as well, with no copying.

As to your gigantic leftovers, I wouldn’t trust the back up software. As noted above, when the backup drive gets full, it will start deleting old files. It would be best to manually burn and check several CDs or DVDs (yes, multiple copies), and then look for cloud storage as well. Keep one physical copy, and put the others in safe places: get a safe deposit box, give to friends or relatives, wherever).

You might notice that I’ve been listening to the horror stories about backups. ( Look up “the winter of our lost content” right here on the board.) All the advice above certainly depends on how much you really want to keep those big files. YMMV.