Neil's Network+ Notes & Tips

Oh man! Ad-blocking software has been detected! :'(

This website is run by the community, for the community... and it needs advertisements in order to keep running. Blocking our ads means your killing our stats!
Please disable your ad-block, or become a premium member to hide all advertisements and this notice.

Nope........they were very easy for me to remember just by reading it straight from the text. What areas are you having difficulty with? No use putting up tables on those, as every textbook has for them. But if you tell me what you're having problems with, then I'll see if I can throw in a "supplimentry" post!

 

Oh man! Ad-blocking software has been detected! :'(

This website is run by the community, for the community... and it needs advertisements in order to keep running. Blocking our ads means your killing our stats!
Please disable your ad-block, or become a premium member to hide all advertisements and this notice.

Just remembering the difference from incremental and differential:-

If you did a full backup on Monday and then on Wednesday the system went down what type of backup would you do to restore the data?

 

UCM.. what type of backup, if any, did you do on Tuesday?

 

The way I got the backup types into my head:

Incremental Backup:

Easy peasy, the backups go in increments, little bits at a time. To use your analogy, if the full backup happened on Monday and your system went down on Wednesday (for the purpose of this we'll pretend your incremental ran on Wednesday before the system went down) You'd require the full backup, Tuesdays incremental backup, and Wednesdays incremental backup.

When you ran your full backup on Monday, you cleared all the archive bits on every file and folder you chose to back up. On Tuesday, everything that has changed since the last full backup is backed up - the backup program knows what has changed because those files will have an archive bit. Once the incremental has backed up those files, it clears the archive bit. On Wednesday, your incremental will backup everything that has changed since Tuesdays incremental. Therefore, to get your system all up to date you need all of your incremental backups since the last full backup because Wednesdays incremental, may not necessarily contain the same files as Tuesdays incremental.

Differential backups work in a different way. Again I'll use your analogy to explain how. On Monday your full backup will run and will clear the archive bit on all of the files and folders you chose to backup. On Tuesday Your differential will run and will backup everything that has changed since the last full backup but it won't clear the archive bit. On Wednesday your differential will run again except this time, it will backup everything that has changed since the last full backup including what changed on Tuesday. So essentially Wednesdays differential backup contains Tuesdays data and Wednesdays data now. As you can imagine, this will take longer to run the backup but the advantage is a much faster restore time as you don't need to keep changing tapes or disks. So unlike an incremental where you'd need every backup to get your system back up, with a differential you only need your last full backup and your latest differential.

Hope that helps matey!

 

No! I'm more confused than i was before

 

This is the problem the question doesn't say, so I am assuming it would of been differential, because the last backup was the full backup? However after reading jay's post. I'm not sure now!

 

Ok, well the question should have stipulated it.

If it was backed up on Tuesday, there are three possible ways. 1) another full backup 2) a differential 3) an Incremental

We don't know if a backup was performed on Wednesday, though i would assume not, as backups are normally performed at the end of the working day when that days work is backed up.

If it was another full backup, then you would only need Tuesdays tape.

In this particular scenario, as there is only one day backed up after the last full backup (ie Tuesday) it doesn't matter whether the backup was incremental or differential. you would need the last full backup tape and the one done on Tuesday.

Jay's explanation is good. i suggest you read it over a few more times and not worry so much about that badly worded question.

 

UCM, a differential backup takes the differenses from the last ful backup.
Let say you do a full backup on friday 20.00 hours and a dif at the time on the other days of the week, the backup on monday contains all files changed since the full backup. Wednesday would contain all files changed since last full backup, so files from monday, tuesday and wednesday.
It can only do this if it recognizes which files have changed and which not. It uses the archive bit for this. So the diff backup does not clear the archive bit.

A incremental back does clear this bit, so inc BU's backup only the changed files since last full backup or incremental backup.

HTH

 

Thanks

 

:hhhmmm..... aah now I understand! Thanks Jay:thumbeft

Rep left

 

I had meant to post this since you asked the question, but ofcourse, I wanted to be thorough, so I took some time to put this together.

Ok, lemme see what I can do here. Based on your scenario, since the last full backup (or "backup" for that matter) was done on Monday, then that's the backup you'll use to restore the data.......cuz you didn't mention any other backups done on Tuesday or Wednesday (before the system went down). However, before we move on, you FIRST need to know WHAT these backup methods actually backup!

Which brings me to........

Backup Types
Yea, you forced me! So let me see how simple and short I can be here. I'll examine the 3 major backup types that you need to know and also touch on a fourth that might probably (least likely) pop up on the exam. They are: Full, Differential, Incremental and Copy.



FULL Backup
The simplest of them all. This does a "full" job by backing up everything and clearing the archive bit. Takes the MOST time to backup (for obvious reasons), but takes the LEAST time to restore.....since "everything" is on one nice backup tape!

DIFFERENTIAL Backup
This backs up everything that was changed/modified since the last Full backup and does NOT change the archive bit. So it doesn't matter if you do a differential backup everyday, because each time you do it, it will only back up all the files that were changed since the last Full backup.....because it doesn't clear the archive bit! In other words, the backup size gets bigger daily and thus, it takes up more time to backup than the previous day. However, in the event of a crash at ANY given time, you would only need 2 backup tapes: the last Full backup and the last Differential backup. Remember that!

INCREMENTAL Backup
This backs up everything that was changed/modified since the last Full or Incremental backup, because this changes the archive bit.....just like the full backup does. This backup takes the least time to do, because it only backs up the files changed for that particular day (considering you do this everyday until your next full backup). However, though its fast to do, it kicks you in the butt when the system crashes! Because you'll need the last Full backup as well as all the other Incremental backups you did (between the last Full) up until the crash. Therefore, this method takes the LEAST time to backup, but the LONGEST time to restore. Remember that!

COPY Backup
This is not likely to show up on the exam, but there's no harm in you knowing it. It does the SAME as the Full backup (backs up everything), but it does NOT change the archive bit. That's all! Simple huh?


Anyways, I've got some scenarios to help you better understand. Let's create a scenario and see the results that differential and incremental backups produce. I'll need my niffty little diagram I made......but you can use it also for reference to see the difference.



Scenario: The same scenario is used for both Differential and Incremental backups (as illustrated in the diagram). Your job is to backup the main server for a business. The business week runs from Monday-Friday. A full backup for the business week is done on Saturdays only (because the boss wants it that way! ). The first gray block on the left of both boxes represents the full backup that was done for the previous week (Week1). The same amount of data is changed/modified in both cases (both Differential and Incremental) for the various days of the current week (Week2). The data changed each day is colour-coded for simplicity. The last block in both cases, shows what the full backup of Week2 looks like. The main server crashes on Friday BEFORE you make your backup for that day. Using the above diagram, let's see how to restore the server if the Differential or Incremental backup method was used in the scenario.

Incremental
As you can see, the backups done for each day are small and take less time, since it only backs up the data changed for that particular day. So since the server crashed on Friday before we did our daily backup, then we would first need our last Full backup (Week1), and then we will need all of our Incremental backups done after that up until the crash -- in this case: Monday, Tuesday, Wednesday and Thursday......for a total amount of 5 backups! Now you see why Incremental backups take the longest time to restore!

Differential
The same amount of data changed per day is used back here in the Differential scenario. As you can see, each daily backup for Week2 backs up the current day's data, as well as the previous day's data. So the backup size gets larger each day and takes more time to do than the previous. However, it pays off when the crash occurs. In this scenario, we'll just need the last Full backup (Week1) and the last Differential backup (Thursday).​

Now you see how the colour-coded data makes it easy to understand WHAT is being backed up. I know this definitely helped out and made you understand how these backups work. Its the SIMPLEST way I could've put it. Happy studying mate!

 

That's a great way of showing it Neil.

My only criticism, is that the full backup, *week two*, would also contain the full backup of *week one* so the column representing it should indicate that

 

WOW! Imagine since I made that last post, NOW was when I actually found the time to revisit! Tight weekend as usual guys.

Thanks for spotting that out Bluerinse, guess I was more concentrating on the current Week2 and it slipped me to add in Week1 . But since I (luckily) structured the last column that way, then the right way to correct it would be to say that:

1. the first half of the last column (the half with the coloured blocks) represents Week2
AND
2. the last half (the gray one) represents Week1........all together in ONE backup file​

So for those who are using my backup scenario (above) for reference, DON'T FORGET TO ADD THIS IN!

 

Network+ Study Resources
I created a separate thread for this. Check it out here: Network+ Study Resources (2005 Objectives) All-in-One Thread!

 

Took a copy of that post for future reference thanks

 

I'm sorry but I need to reply to this very old post.

Neil, you are a genius, the cable specs post was really easy to understand and I like to thank you for taking the time to do it.

EDIT: I should have read the rest of the pages. I guess I will have to check the info provided by Neil... =(