Redundancy for Data
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35 hours 25 minutes
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>> Now a few sections ago we talked about RAID,
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Redundant Array of Independent Disks or Devices.
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We said that varies.
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But the idea behind RAID
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is it protects us against a hardware failure.
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It doesn't provide data redundancy that we need
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because if malware were
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to infect OneDrive in a RAID array,
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it would affect them all.
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We have to make sure that we have data backups,
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which really is our primary means
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for having redundancy of data.
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We'll look at in this section the redundancy,
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and then we'll talk about
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>> the different types of backups.
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>> We can have full, incremental,
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differential, and we'll also talk about copies also.
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Like I said, your data,
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that's one of our primary resources
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and we want to be able to restore our data in
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the event of a failure like a hard drive
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certainly in the event of a disaster like a hurricane,
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fire, flood, and
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then we also consider things like malware,
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or corruption, or any of the numerous ways
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that our data can lose its integrity.
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When we talk about backups,
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there are different types we
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can run and what I'm talking about
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here is primarily in the realm of Windows.
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But let's talk a little bit about how backups happen.
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You have built-in applications for
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Windows systems or you can buy
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>> third-party applications.
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>> But the way in Windows systems
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it's determined whether or not a file needs
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to be backed up is it has a bit called the archive bit.
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That archive bit, you can think of it
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just as a flag that says, "Hey.
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I've changed back me up."
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When you run your system backup,
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anything with the flag sense is going to get back down.
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When I do my full backup once a week,
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everything with that archive bit gets back down.
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The backup backs up everything and
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then it clears the archive bit.
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Essentially, that's the way of
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saying everything is taken care of,
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backed it all up.
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Now, the thing about
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a full backup though is it can
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take a lot of time to do a full backup.
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It can take a lot of media.
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You need a lot of storage space,
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and you generally don't want to be
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backing up data while users are working on the drives.
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There are ways around that, that's not critical.
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But as a general rule,
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we are not going to do 15 hours with backup a night.
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As matter of fact,
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you could have it take
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30 hours to back up one day worth of data.
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It takes longer than that.
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We want to use our full backups,
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but we have to combine them usually
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with incremental or differentials.
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Now, incrementals backup everything that's
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changed since the last backup of any kind.
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Differential backups,
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backup everything that's changed since
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the last full backup.
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For instance, let's say I do full on Sunday.
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Files change on Monday.
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Monday's incremental backs up which's changed?
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Clears the archives bit,
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so everything is been backed up.
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But Tuesday morning files get change and
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the new archive bits pop-up will
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choose this incremental backs
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up everything that's changed that day.
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Clears the bit, wins this incremental,
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new files change,
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their archive bits popup, Wednesday.
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Wednesday's incremental backup or resets all the bits.
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Your incremental backups and your full backups,
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reset the bits afterwards.
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What that means is we're not going to
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go back and pick up things
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that have already been backed up,
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so you get a quicker backup.
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Actually, that's not the best way to say it.
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Yeah, that's probably good.
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I'll get a quicker backup.
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The thing though about an incremental backup
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is because it only backs up each day's files.
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When you need to restore,
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you have to go back to the full,
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then you have to restore Monday state,
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Tuesday state, Wednesday state to
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get back to the point where
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you have everything that could have been lost.
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That incremental backup backs up what's changed
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since the last backup of
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any kind whether it's full or incremental.
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Now the differential backup
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is different than the other two,
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it does not clear the archives bit.
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Monday's differential backs up
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what changed in Sunday's full.
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Tuesday's differential backs up
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what's changed since Sunday's full.
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Wednesday's differential backs up
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what's changed since Sunday's full backup.
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When I have to do a restore on Thursday,
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I get a quicker restore.
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All I have to do is restore Sunday's
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full and the most recent differential,
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and I'm back to full operations.
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The incrementals a little quicker to
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backup but it's slower to restore,
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and differential is just the opposite.
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It all has to do with that archive bit.
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If the archive bit is set,
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then the files are going to get backed
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up and it depends on
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what type of backup is going to
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happen as to whether or not the bit reset.
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I will mention there are a couple of ways
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they could allude to that on the exam.
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If the archive bit is set to one,
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that's an indication that the file
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>> needs to be backed up.
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>> They might say, which form
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of backup resets the bit to zero.
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Anyone that resets the bit,
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that's saying, "No, this doesn't need to be backed up."
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So both full and incremental reset the bit to zero.
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Or you could hear them describe differential is saying,
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"Sets the bit to one or doesn't change
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>> the bit from one."
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>> Basically, resets the bit
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full and incremental, doesn't reset differential.
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One additional thing to consider here.
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Let's say that it's four o'clock in the afternoon and
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I'm getting ready to install
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an update maybe and I decide,
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hey, I better do a quick backup
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before I do this update just in case there's a problem.
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Well, I want to back up the full system,
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but if I do
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a full backup that will reset the archive bit.
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What that means when I do
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my nightly backup at midnight or whenever it is,
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it's not going to have the complete day's data.
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It's only going to have what's changed
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since four o'clock when I did that backup.
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In order to make sure
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my nightly backup contains
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>> the full day's worth of data.
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>> I'll do a copy.
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Anytime I do a backup on the fly
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>> and unscheduled backup,
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>> it should be a copy.
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With the copy, it doesn't look for or
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reset the archive bit but
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I could use it to back up the entire system.
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Anytime you do a backup on the fly,
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a copy backup is the best way to go about it.
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Now, don't forget, you need more than
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just the type of backup
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to be determined in your strategy.
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We've got to figure out, first of all,
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what needs to be backed up.
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I know that sounds very basic,
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but yeah, that's our first step.
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What's are we going to backup?
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Then we want to make sure that we
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have a rotation scheme for
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our media so that we're not recording
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today's backup over yesterday's tapes.
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There are a couple of different media
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rotations you can look them up.
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I don't think they're testable,
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but there's one called the Grandfather-Father-Son,
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which basically just means long-term,
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mid-term, and short-term backups.
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Then the Tower of Hanoi media rotation scheme
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requires seven backup tapes.
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I don't know Finney if you've played
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the Tower of Hanoi, the game.
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But they swear to me if you'd played the
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>> Tower of Hanoi,
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>> the backup strategy would make sense.
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But if you haven't,
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it seems a little bit strange because you have
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seven individual backups and
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you use those tapes rotating on a basis.
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Again, they promised me it makes sense.
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I'm not 100 percent convinced of that.
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I've always been more fan
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at the Grandfather-Father-Son method.
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We got to figure out the media rotation.
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I've got to figure out how often we
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need to backup and how often I need to
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backup is going to be a direct result
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of what my recovery point objectives are.
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How much data am I willing to lose?
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You have to take all of
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these considerations in when
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we're determining our backup strategy,
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specifically in relation to timing.
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We've got a backup our data so that
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we get that additional redundancy.
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But we also have to remember that
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>> the different types of
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>> backups will impact what
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we're able to restore and how quickly
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