Confused about full and diff backups

[blong]

Sorry i am a big noob in regards to backups. Hope you guys can help me.

lets say I have a backup system like this:

1. Full backup weekly (sat), overwritten after 4 weeks.
2. Diff backup daily (mon-fri), overwritten after 7 days.

All are backup to a network NAS. Full backups to a folder called "full backup" and diff backups to a folder called "diff backup".

And I would like to have a safe copy offsite (maybe like once per mth), using dropbox or something. Might I know if I want to ensure that I have a complete copy of my backups, can I transfer the full backup (from the full backup folder) and then one of the latest diff backups (from the diff backup folder)?

Is this correct?

 

[davidktw]

Sorry i am a big noob in regards to backups. Hope you guys can help me.

lets say I have a backup system like this:

1. Full backup weekly (sat), overwritten after 4 weeks.
2. Diff backup daily (mon-fri), overwritten after 7 days.

All are backup to a network NAS. Full backups to a folder called "full backup" and diff backups to a folder called "diff backup".

And I would like to have a safe copy offsite (maybe like once per mth), using dropbox or something. Might I know if I want to ensure that I have a complete copy of my backups, can I transfer the full backup (from the full backup folder) and then one of the latest diff backups (from the diff backup folder)?

Is this correct?

Depending on whether you are using incremental diff, or full diff. For the former, you need the last full + all other diff up to the day you are trying to restore. For full diff, you need the last full + the actual diff on the day you are trying to restore.

Offsite you can copy a copy of each and store elsewhere. I'm not too sure if backup software does it automatically ?

 

[blong]

It does not automatically do the offsite backup. That is why I am a bit confused which bkf file to copy to. I assume that the backup software (Symantec Backup Exec 12) knows which backup is a "full backup" and will use that when (and if) there is a need to restore.

 

[davidktw]

It does not automatically do the offsite backup. That is why I am a bit confused which bkf file to copy to. I assume that the backup software (Symantec Backup Exec 12) knows which backup is a "full backup" and will use that when (and if) there is a need to restore.

I believe offsite or not has little to do with which backup methodology you are configuring, isn't it ? In your backup scheme, do you get to specify offsite as an option or an feature in the scheme ?

 

[Pokémon]

Firstly, you need to understand what differential (incremental) backup is. A differential backup is a type of data backup that preserves data, saving only the difference in the data since the last full backup (Taken from Wiki through searching with Google).

As davidktw had already mentioned, for a restore with differential backup, you will need the full backup, as well as all the differential backups that took place after that full backup. It will be useless with the latest copy of differential backup only if there are a few more before it, or any one corrupted will deem the others useless as well.

In the past, backup medias were expensive, and takes some time for full backup. If the time taken for full backup is not too long, and you have the space to hold 30 days of full backups, go for it.

 

[Asure7]

Huh? I think you have confused incremental vs differential.

E.g. U have one full backup.

If u have differential backups after that,
i.e D1 (for day 1), D2, D3... D10.
If I want to restore data from day 10, u only need the full backup + D10. U don't need D1-9.
Differential backup = each file contains the difference from the last full backup.

However if u have incremental backups,
i.e i1, i2,...... i10.
To restore day 10, u need The full backup + ALL the increments i1 to i10.
Incremental backup records only the difference from the last incremental backup.

Although some references classify incremental as a "subset" of differential, most backup software will just ask u to choose incremental or differential. In those cases, to avoid confusion, differential will mean full differential.

 

[dreant]

 

[dreant]

And I would like to have a safe copy offsite (maybe like once per mth), using dropbox or something. Might I know if I want to ensure that I have a complete copy of my backups, can I transfer the full backup (from the full backup folder) and then one of the latest diff backups (from the diff backup folder)?

Is this correct?

Ideally, you should arrange to have all backups stored (and rotated) offsite. This is usually done with rsync.

What NAS do you have? Some of the newer units have rsync built in, and can mirror a directory onto another similar model nas stored offsite.