Confusion about Backups

veritas_libertas

I am studying for to take the Network+ near the end of June or early July. I am confused about Backups. My professor has tried explain to us about backups and the archive bit, but I still don't understand this. What is this bit? I am also confused about what a Differential backup is. I understand what a full and incremental backup are.

Plantwiz

TechExams.Net - N10-003 Network+ TechNotes, the PDF version


Backup Basics and Different types of backup -- Debian Admin

Full, Incremental, Differential, Stack backup types built-in D_back software

Backup4all 3

Backup/Recovery - The Archive Bit And Incremental Backups on Windows Filesystems

veritas_libertas

I looked at the hyperlinks you sent but I still don't understand the difference between differential and incremental backups. They look like the same thing.

sprkymrk

Full= backup everything every time.

Differential = backup everything that has changed since the last full backup.

Incremental = backup only what has changed since the last backup of any type.

So if you do a full backup on Monday, then on Tuesday, Wednesday and Thursday do a differential, here is what your backup would look like:

Monday= everything.
Tuesday= only Tuesday's stuff.
Wednesday = Tuesday and Wednesday's stuff.
Thursday= Tuesday, Wednesday and Thursday's stuff.

Thus to do a restore on any particular day you only need the full backup from Monday and the last differential backup. That's 2 tapes let's say. So on Friday you need Monday and Thursday tapes to do a restore.


However, if you do a full backup on Monday, followed by an incremental backup on Tuesday, Wednesday and Thursday, here is how your backups would look:

Monday = everything.
Tuesday = only new/changed stuff since Monday.
Wednesday = only new/changed stuff from Tuesday.
Thursday = only new/changed stuff from Wednesday.

This makes for much faster backups than a differential. However, in order to do a restore, you need the full backup and ALL incremental backups up to the point of the restore. So to do that same restore on Friday now you need all 4 tapes, Monday's full and Tuesday, Wednesday and Thursday's incrementals. That makes it much longer to do a restore than with differentials.

Hope that makes sense, I'm in a bit of hurry as I hammer this reply out.

Plantwiz

Not sure what you don't get but if the links plus sprkymrk long explaination don't help.....

veritas_libertas wrote: »

I looked at the hyperlinks you sent but I still don't understand the difference between differential and incremental backups. They look like the same thing.

You are not enrolled at PCPros or something like that are you?


It may just mean you need to build yourself a lab and try these things out. Most people here have done that. You'll need some experience before you take the exams or all you are doing is memorizing facts and that doesn't make the candidate an asset in the field.

Get some old hardware and start setting up a small network and testing these things out. Used hardware is cheap and still valuable to use for practice purposes.

Do you have any experience? OR just decided to sign up for a class?

veritas_libertas

Plantwiz wrote: »

Not sure what you don't get but if the links plus sprkymrk long explaination don't help.....





You are not enrolled at PCPros or something like that are you?


It may just mean you need to build yourself a lab and try these things out. Most people here have done that. You'll need some experience before you take the exams or all you are doing is memorizing facts and that doesn't make the candidate an asset in the field.

Get some old hardware and start setting up a small network and testing these things out. Used hardware is cheap and still valuable to use for practice purposes.

Do you have any experience? OR just decided to sign up for a class?

No, I am at a Community College in my town. I graduate this summer thanks to an Accounting class that I have to retake I am then transferring to the University of South Carolina where I plan to get my Bachelor degree in Network Security.

The backup thing drives me nuts probably because I don't understand why it is the way it is. Why not just full or differential, what is incremental? Why is it different? I know I am missing something simple but I don't know what it is.

veritas_libertas

sprkymrk wrote: »

Full= backup everything every time.

Differential = backup everything that has changed since the last full backup.

Incremental = backup only what has changed since the last backup of any type.

So if you do a full backup on Monday, then on Tuesday, Wednesday and Thursday do a differential, here is what your backup would look like:

Monday= everything.
Tuesday= only Tuesday's stuff.
Wednesday = Tuesday and Wednesday's stuff.
Thursday= Tuesday, Wednesday and Thursday's stuff.

Thus to do a restore on any particular day you only need the full backup from Monday and the last differential backup. That's 2 tapes let's say. So on Friday you need Monday and Thursday tapes to do a restore.


However, if you do a full backup on Monday, followed by an incremental backup on Tuesday, Wednesday and Thursday, here is how your backups would look:

Monday = everything.
Tuesday = only new/changed stuff since Monday.
Wednesday = only new/changed stuff from Tuesday.
Thursday = only new/changed stuff from Wednesday.

This makes for much faster backups than a differential. However, in order to do a restore, you need the full backup and ALL incremental backups up to the point of the restore. So to do that same restore on Friday now you need all 4 tapes, Monday's full and Tuesday, Wednesday and Thursday's incrementals. That makes it much longer to do a restore than with differentials.

Hope that makes sense, I'm in a bit of hurry as I hammer this reply out.

Do I understand this to mean that an incremental backup is only for a single day's changes and not for every thing since a full backup?

Plantwiz

veritas_libertas wrote: »

....

The backup thing drives me nuts probably because I don't understand why it is the way it is. Why not just full or differential, what is incremental? Why is it different? I know I am missing something simple but I don't know what it is.

Are you kidding me? Really?

sprkymrk wrote:

Full= backup everything every time.

Differential = backup everything that has changed since the last full backup.

Incremental = backup only what has changed since the last backup of any type.

INCREMEMTAL

sprkymrk wrote:

However, if you do a full backup on Monday, followed by an incremental backup on Tuesday, Wednesday and Thursday, here is how your backups would look:

Monday = everything.
Tuesday = only new/changed stuff since Monday.
Wednesday = only new/changed stuff from Tuesday.
Thursday = only new/changed stuff from Wednesday.

This makes for much faster backups than a differential. However, in order to do a restore, you need the full backup and ALL incremental backups up to the point of the restore. So to do that same restore on Friday now you need all 4 tapes, Monday's full and Tuesday, Wednesday and Thursday's incrementals. That makes it much longer to do a restore than with differentials.

VS.

DIFFERENCTIAL

sprkymrk wrote:

So if you do a full backup on Monday, then on Tuesday, Wednesday and Thursday do a differential, here is what your backup would look like:

Monday= everything.
Tuesday= only Tuesday's stuff.
Wednesday = Tuesday and Wednesday's stuff.
Thursday= Tuesday, Wednesday and Thursday's stuff.

Thus to do a restore on any particular day you only need the full backup from Monday and the last differential backup. That's 2 tapes let's say. So on Friday you need Monday and Thursday tapes to do a restore.

You did read what sprkymrk typed up right?


1 uses the full back up plus the last tape. The other uses the full back up plus all the tapes up to the time you want to restore to.


-Full backup (if done every night) is VERY LONG (and usually unnecessary)
-Differential is long one night, but not as long the other nights, but grows in time each night...due to more data being stored.
-Incremental is long one night, but quick the other nights as only the changes are backedup....the restore process is longest.


If it still doesn't makes sense....just drop it and move along to something else. You really need to get some expreince with it because it is not very difficult.

If backups are confusing, why would you select the name vertias?

veritas_libertas

Plantwiz wrote: »

Are you kidding me? Really?






INCREMEMTAL


VS.

DIFFERENCTIAL



You did read what sprkymrk typed up right?


1 uses the full back up plus the last tape. The other uses the full back up plus all the tapes up to the time you want to restore to.


-Full backup (if done every night) is VERY LONG (and usually unnecessary)
-Differential is long one night, but not as long the other nights, but grows in time each night...due to more data being stored.
-Incremental is long one night, but quick the other nights as only the changes are backedup....the restore process is longest.


If it still doesn't makes sense....just drop it and move along to something else. You really need to get some expreince with it because it is not very difficult.

If backups are confusing, why would you select the name vertias?

First of all the name is Veritas. Latin for Truth. I don't claim to be a brainiac.

I was hoping for help and not an intellectual bashing. Thanks though, I shall go on.

skrpune

veritas_libertas wrote: »

Do I understand this to mean that an incremental backup is only for a single day's changes and not for every thing since a full backup?

almost - it would be for a single day's changes if and only if you do incremental backups every day, which is not always the case. An incremental backup takes care of everything that's changed since the last incremental OR full backup, whichever type was the last backup type.

Basically, the archive bit is a little "flag" of sorts that signifies that there has been change to data and that it needs to be backed up. When you do a full/normal backup, it backs up all the selected files regardless of the archive bit setting, and it sets the archive it on all the backed up data to the off position.

Differential backups do not reset the archive bit to off, backup everything since the last full backup, take longer to backup, but are quicker and easier to recover; incrementals back up only data with the archive bit set to on (i.e., only what's changed since the last incremental or full backup) reset the archive bit to off, take less time to backup, but take longer to recover.

I would venture to guess that the main reason there are different backup types is so that there is flexibility in creating a backup plan that works for the specific situation at hand. If you need to have quick backups during the week but don't care how long it takes to do recovery, then full once a week plus incrementals every day or every other day would be best. If you don't care how long it takes to back up but want to be able to recover more quickly, then full plus differentials would work best. Having different backup types allows for flexibility in planning backup schedules in a variety of situations.

Plantwiz

skrpune wrote: »

I would venture to guess that the main reason there are different backup types is so that there is flexibility in creating a backup plan that works for the specific situation at hand. If you need to have quick backups during the week but don't care how long it takes to do recovery, then full once a week plus incrementals every day or every other day would be best. If you don't care how long it takes to back up but want to be able to recover more quickly, then full plus differentials would work best. Having different backup types allows for flexibility in planning backup schedules in a variety of situations.

Exactly!


Some businesses cannot afford to stop production to have complete backups each night. Others can.

Some cannot afford to be down for a few hours while the server that crashed is being restored.....others can.

It just depends.


If you can keep all the employees off the network to backup the server(s), then you use what makes the most sense for backup vs. restore.

If you have a network that operates 24/7...then the risk needs to be considered (and likely there are mirrored servers in that case), but you figure the best combination for what the client can risk....your time doing a reinstall and paying employees to sit around....or extra tape media (or disk space) and staying off the nework so the files needing backup are stored with the most recent copy in reserve.

veritas_libertas

Thanks guys. I think I have it now. I appreciate your time . Back to the books....