Differential / Incremental Back-ups?

Legacy User

Anyone help with the above in layman terms (keep it simple stupid) just reading through my coursework and am not too sure of the difference they both sound the same? and where does the archive attribute come into it? Any help appreciated. Cheers Kweelo

Webmaster

Here is an excerpt of an explanation from one of our Windows 2000 Server exams.

Some backup types use backup markers, also known as archive attributes, to track when a file has been backed up. When the file changes, the OS marks the file to be backed up again. Files or directories that have been moved to a new location are not marked for backup. Backup allows you to choose to back up only files with this marker set, and you can choose whether or not to mark files as having been backed up.
There are several factors to consider when deciding what backup to use, including the following issues:

• The normal backup, or full, type is best when a large amount of data changes between backups or to provide a baseline for the other backup types. Normal backups files are easy to find because they are always on a current backup of your system or on one medium. The disadvantages of normal backup are that it is time-consuming and can be redundant if files do not change frequently.

• The incremental backup type is best to record the progression of frequently changed data. Incremental type clears the flagged folders and files it backs up and acquires the new changes on the next backup. Incremental backups require the least amount of data storage space and are the least time-consuming. However, incremental requires several rollbacks plus the full to acquire a complete accurate restore of the backed up data.

• The differential backup type simplifies the process for restoring files. Differential type will not clear the flagged folders and files it backs up and on the very next backup will acquire the same files plus any changes. Differential Recovery requires only the last normal backup medium and last differential medium to restore the data to normal. If large amounts of data change daily, differential backups can consume more time than incremental backups.

• Copy backup type backs all selected files and folders however it neither looks for nor clears markers on files and folders. This type of backup would be good for a snap shot between a full and an incremental.

To provide for long-term storage with fewer media, you can use a combination of a normal backup plus either incremental or differential backups.

I hope this answers your question

Johan

jpmcginty

I think the key point here is the archive tag. Basically if a file is changed it sticks its hand in the air to tell the OS that its changed. The OS then has a choice of backing it up and tell the file to put its hand down or ignoring the hand so the next time it checks it backs it up again and again and again. so all you need to know which backup tells the file to put its hand down and which ignores the hand. its over to you...

(at least I think thats what the archive does: if in doubt run it overnight and do a test restore...)

ucanbbreached

guest check this out. I had a little time spent trying to sort the differences with this also. Something that eluded me, which seems to be a part of your case also, is the archive bit. Windows provides a good description.
In windows select a file and click properties. At the bottom you will find a check box next to the word archive. 2000 or NTFS have to click advanced tab and it will be listed as the very first option

This is the feature in windows that sets the archive bit for backups.

select the archive bit, if not already, close properties and the window

now back up the file with the accessories-->system tools-->backup feature

in the backup dialog select the option to backup only a certain file; do not select any advanced options

now go back and check the archive bit on the same file, it will be unchecked

This is what happens on the incremental backup. with a differential
the archive bit will still be checked.

Hope this helps,
ucan

jpmcginty

heres a tip on telling the difference between incremental and differential that should help:

differential back ups DONT differentiate
incremental back ups do

ie ARCHIVE = ON
differential : backup and that will do (stays ON)
incremental: backup and I had better make sure I don't do that again (turns OFF)


[Proviso: this may be of no help]