now, another super important idea when it comes to the world of redundancy is providing redundancy for a data. So we normally think about backing up our data to tapes or some other form of media. So ultimately, if you have a hardware failure, we want to get our data back.
Now they're several different types of backups and these air always testable. Ah, you have a full incremental differential and copy. Now full backup is the easiest to understand.
A full backup just couldn't back up everything. That's easy enough
now. The incremental backup is used in conjunction with the full,
so uninterested a ll backup is gonna back up everything that's changed since the last backup of any kind. So we do a full backup on Sunday. Monday's incremental backs up. What changed since Sunday.
Tuesday's incremental backs up with change since Monday,
Wednesday's incremental backs of what's changed since Tuesday, so that when we do have to do restore, we have to restore the last full and then each day's incremental sze now differential backs up, which changed since the last full backup.
So you do your full back up on Sunday Monday, things change the differential backs up, which changed on since the full on Sunday. Tuesday backs up what's changed since the full on Sunday.
Wednesday backs up with change since the full on Sunday. So when you have to do a restore and you've done differentials, you only have to restore to tapes. Definitely testicle. So the idea is, Do I want to save time backing up or doing a safe time? Restoring the quickest restore is gonna be the full
right. The slowest for store is gonna be the incremental because we have to do the full and then every single day. So, you know, those were some ideas. Now the way this is determined at least in Windows system is there's a bit called the archive bit
and the archive. It's like a little flag that when a file change, that archive bit pops up and says, Hey, I've changed back me up.
So when we do that full backup on Sunday night or whatever, all the archive bits air cleared. It's like they've been mowed down.
Hey, and Monday morning we come in, files start to change. Well, the flag pops back up
Monday night's incremental wipes all the flags as well clears the archive bits. So Monday night incremental is done. All the archive bits air cleared. Then on Tuesday, as files get creative modified, the archive bits pop up and Tuesday nights incremental
backs up. Just what's changed on Tuesday
clears the flags. Wednesday files change. Our Cabinet pops up when say, Not back up Just what's changed on Wednesday. Okay, so both the full and the incremental clear the archive bit.
The one that's different than the other two is a differential backup. It does not clear the archives bit. That's why we do that back up Monday. And then we come and do back up Tuesday, and we're still backing up everything that changed since Sunday because none of the bits have been reset or flavored.
Now, one thing worth mentioning is a copy. Backup can back up the system in its entirety,
and it does not clear the orcas if it doesn't care about the archives bit
for that purpose. If you're doing a back up on the fly
unscheduled back up, you want to use a copy because think about it. Let's say I'm getting ready to install a service packing, I think. Well, I better do. Um, I better do back up.
Well, if I do a full back up, it's gonna clear the archive bit.
So at midnight, when I run my normal back up, nothing's gonna be on there. So in order to maintain the integrity of our nightly backups when you do an unscheduled backup, you do want to make sure it's a company.