Windows Backup 1

[lmoe]

I find the terms for Windows Backup confusing.
Incremental, Differential, etc.

Which one keeps all the unchanged files and just backs up the changed files -- but does not keep multiple versions of any file?

I need to make a backup I am doing run faster than it does.



LMC
IT/MIS
"Never stop learning.

 

[bcastner]

As far as I know differential and incremental are interchangeable terms and mean what you want to do: copy only new and changed files that differ from a core backup set.

Make sure you occasionally due a full backup set. There is nothing more annoying and error prone than doing a restore from thirty incremental backup sets.

 

[bkrike]

Here is a link from Bcastner:
thread779-893988

bcastner (IS/IT--Manageme) Aug 4, 2004

http://www.2brightsparks.com/syncback/

I have found the freeware he recommended in the above link (Syncback) to work without flaw, and it completely simplified my back up process.

 

[lmoe]

bkrike -- the xcopy link was nice, except it left out /d I think.

bcastner -- If both copy ONLY new and CHANGED files, why would I need to restore from multiple sources?

1. Backup to a disk (Iomega 35 gig cartridge) labelled Monday. Its new, so the backup is complete.

2. On Tuesday to Friday I back up to those cartridges.

3. On Monday I come back to the original.
Are you saying Backup will see if the file on Hard drive is new rather than compare the file on the hard drive to the file on the cartridge?

If so, that explains what you said.


LMC
IT/MIS
"Never stop learning.

 

[bcastner]

The backup programs usually work by looking to an archive attribute on the hard disk for each file. When a file is created or changed, the filestore sets the archive attribute.

An incremental or differential backup does not usually look to a catalogue of file details for what it has backed up; rather it resets the archive attribute of all files when the backup is completed. It only need query the filestore for any new or changed files by examing the archive attribute. It then backs up these new or changed files, and resets the filestore archive attribute to prepare for the next session.

Hence doing a restore using incremental backup sets involves:
. Restoring the base or core set of files
. Restoring Incremental backup sets #1, #2, #3... etc.

It needs to do this because a file could have been modified on each day the incremental backup was run. Or a file could have been modified only on Day #1, but not touched on any subsequent day.

 

[wcburton]

Differential does not reset the archive bit on the file but incremental does. Differential = what is different from the last full. Incremental = little bit one day, little bit the next day, and so on.

Consider this:
Full backup on Sunday.
FileA changed on Monday.
FileB changed on Tuesday.

Differential would backup FileA on Monday and both files on Tuesday. Full restore on Wed would require only Sunday and Tuesday backups.

Incremental would backup FileA on Monday, reset the bit, and only backup FileB on Tuesday. Full restore on Wed would require all 3 backups.

If the same files change during the week (or the same large files which take more time to backup), then go ahead and use differential backups. It would be quicker to restore.

One more consideration:
FileA (1 MB) changed Monday.
FileB (1 MB) changed Tuesday.
FileC (150 MB) changed on Monday and again on Tuesday.

Doing a full restore from incremental would require 2 runs of 151 MB (after the full backup was restored of course). Doing a full restore from differenial would only require one run of 152 MB.

 

[bcastner]

wcburton,

Yes, that helps and makes the distinction much clearer for me.

This site also helped:

http://www.backup4all.com/backup_types.php

 

[lmoe]

I got this all. But it seems like someone missed the point.
It would be cleaner if:

FileA changed on Monday -- Full backup to existing backup.
FileB changes on Tuesday -- Full backup to existing backup.
This also backs up FileA because FileA on PC is newer than FileA on tape or backup device.

Then, back ups are faster and you only need to go to the newest tape to restore.

Xcopy /d works like this.

LMC
IT/MIS
"Never stop learning.

 

[wcburton]

A backup is not mounted as a file system that you can update, especially if you are writing to tape. You can use xcopy to make backup copies of files to a rewritable medium such as another hard drive or a CDRW or DVDRW. There have been programs that will mount a tape as a file system but they are *extremely* slow.

The other thing with the xcopy style backup is that you do not get some files that are open or certain system files. You also cannot restore system files without having a proper backup program.

When you use a regular backup program (not xcopy), the previous contents of the tape are either overwritten or another backup set is appended to the tape but the previous backup set is never just updated.

 

[lmoe]

Thanks, all...found the problem.
The backup was going to an iomega external drive with 35 gig cartridges.
When we switched the backup so it backed up to the c: drive the speed issue vanished.
We then xcopy the backup to the cartrigdes.
==================
However, I am testing syncback. Thanks for that lead.

LMC
IT/MIS
"Never stop learning.