Backup Exec 12.5, problems with differential backup

[temporaryuser]

Hi all,

Recently been doing a full backup every day for 1TB of data. It takes 20 hours and is not best practice.
I have decided to use the differential backup during weekdays and do the full backup on the friday. I am using the same selection list and using the modified time option but the differential backup just won't work! Instead of only backup files that have changed since the last full backup it just runs a full backup! I know this because the tape I use will fill up and request that I insert more media. There is no way that the files that have changed amount to 200+ GB.

Am I missing something?

Thanks,

Luke.

[Chris_L1]

Hi Luke, Differential backup is not the best way to backup only the cahnged files in your environment. I would advise you to use Incremental instead, because Incremental backup uses so called - archive bit. This archive bit is being switched on every time a file is changed, and when this file is being backed up, the archive bit is turned off. Differential backup does use this archive bit, and only copy the files selected for backup. Use Incremental insted of Differential ( e.g. if your full backup runs Friday, and you have Incremental backup jobs every night, you'll backup only the files that have been changed since the las full or incremental backup. Hope this helps.

[temporaryuser]

Hi Chris,

The reason we don't use incremental is because we cannot use the option for the archive bit. I also fear it would have the same result as what is happening with the differential backups. We backup a snapshot of our file server and this cannot be backed up using the archive bit hence we run the full backup using modified time and the differential using the modified time. We are trying not to use incremental because we feel it makes for a difficult restoration as we need every incremental tape and the full backups where as we only would need the latest differential tape and the full backups. We are trying to keep things as simple as possible.

Thanks,

Luke.

[Chris_L1]

Ok, so I can assume that you do not use a NAS storage to store incremental or differential backups? In such a situation I would advise that you spent some money for disk storage so you can implement very fast and efficent solution, called Advanced Disk Based Backup Option (ADBO), which can signifficantly reduce the backup window time. As per http://seer.entsupport.symantec.com/docs/299384.htm your benefist are:

The Symantec Backup Exec for Windows Servers Advanced Disk-based Backup Option (ADBO) is installed as a separate, add-on component of Backup Exec for Windows Servers.

The Advanced Disk-based Backup Option provides the following features:

Synthetic backup. This feature uses a policy to enable a full backup to be assembled, or synthesized, from a baseline and subsequent incremental backups that are also contained in a policy.

The benefits of using a synthetic backup include the following:

• A reduced backup window since the synthetic backup can be scheduled outside of the time-critical backup window.
• Reduced network traffic since the synthetic backup does not need to access the network.
• True image restore. This feature enables Backup Exec to restore the contents of directories to what they were at the time of any full or incremental backup.
•  
• Restore selections are made from a view of the directories as they existed at the time of the particular backup. Files that were deleted before the time of the backup are not restored. In true image restore, only the correct versions of files are restored from the appropriate full or incremental backups that contain them. Previous versions are not unnecessarily restored and then overwritten.
• Offhost backup. This feature enables the backup operation to be processed on a Backup Exec media server instead of on the remote computer, or host computer. Moving the backup from the remote computer to a media server enables better backup performance and frees the remote computer as well.

[temporaryuser]

So are you saying its impossible to do incremental/differential backups on tape in Backup Exec 12.5? What i'm doing should work unless I have missed something somewhere or I haven't properly configured a setting! I have no money which is why I am using tapes lol!

[Chris_L1]

Mate, I'm not saying that your scenario is impossible, but what you are trying to achieve is impossible without ADBO option. You are already doing differential backup on tape, so it is already possible. I'm suggesting this option for significant speed and performance improvements (this is what you are asking for). It's entirely up to you what in-house backup strategy you are going to implement, but don't expect plain Backup Exec 12.5 to do miracles...

[temporaryuser]

All I want is to get the differential backups working so it backs up only the changed files since the last full backup. Right now it backs up everything in the selection list. The reason why we are changing to differential during the week is to save time. Budget wise, the only option available is to get the differential working because I cannot afford to purchase a disk array or the agent. Please understand that all I want to do is get the differential working like it is supposed to.

[Chris_L1]

Just for refference, here is a short explanation of what Differential backup is:
A differential backup is a backup of every file on a file system which has changed since the last full backup.
     The alternatives to a differential backup are incremental backup and full backup. A differential backup can be an optimal middle-ground between a full backup and an incremental backup. A differential backup is not as fast as an incremental backup, but it is faster than a full backup. A differential backup requires more storage space than an incremental backup, but less than a full backup. A differential backup requires more time to restore than a full backup, but not as much time to restore as an incremental backup. If you perform a full backup on Sunday and a differential every night, and the system crashes on Thursday, you will only need to restore the full backup from Sunday and the differential backup from Wednesday.

In contrast, if you perform a full backup on Sunday and incremental backups every night, when the system crashes on Thursday, you will need to restore the full backup from Sunday along with the incremental backups from Monday, Tuesday, and Wednesday.

You said that your daily backup is slow and space consuming and that is from your backup strategy. No way to increase your speed if you don't change your backup strategy...Hope this helps. 

[Doa-Fan]

I have to make backups for day of all my SQL Databases and just want to backup only the changed files, so for I just readed here the best way to do this is by using the Incremental option instead the Differential, right ?, already made a few tests with the differential and only saved me the differences but not the original size of my database ...



... just checked a restore of one of my lasts backups and the DB, its original size is 18 GB, so am gonna make a Incremental and see what happens.

[Chris_L1]

Backing up a database is completely different case my frend. The best practise says that you should perform full backup in small to mid-size environment every day. In your case, you have 18 GB database (which is quite big) and this would not apply for you. In mid-sized environments, consider running a weekly full database backup and daily transaction log backups along with daily differential backups except on the day when the full backup is run. Open BEWS 12.5 Admin Guide and read pages from 1352 trough 1356. They will help you decide what backup strategy to use in your environment, because I am not familiar with your in-house setup.

[temporaryuser]

I am aware of the difference between a differential and an incremental and the reason I choose differential is for the faster restore. At the moment I am running a FULL backup every day. That is the daily backup. What I intend to do is a differential backup every day with a full backup at the weekend. The reason why this has not been implemented fully is because the differential backup does not work! Time isn't an issue if the differential backup would work! 1TB of data in the selection list. Approximately 1/8 of the data changes every day. When I was in the testing process it was asking for more media after about 200GB. When I checked where the backup had got to when it stopped I found that it was backing up every file. This is the differential not working because it is backing up EVERY file not just the CHANGED files. I'm sorry if you have misunderstood but i'm trying to make this as clear as possible. Have I missed a setting or configured the job setup wrong? Can you please explain how to set-up a differential job. I do not wish to purchase any agents or hardware. I do not wish to have differential and incremental to be explained. I only want to know where I am going wrong.

Thanks,

Luke.

[temporaryuser]

The differential will not take more than 12 hours which is all I need for a successful backup

[Chris_L1]

I know what you mean, but It's just how differential backup works. I've searched in other forums and I found very similar forum threads connected with your problem. Try using - Differential, use modified time, may be you will have some partial success. That's my last suggestion :)

[temporaryuser]

I am using the modified time option. Its in my first post. Can you explain to me how to setup a differential job so I know I haven't missed anything.

Thanks,

Luke

[EM-Pulse]

I don't know if you've already tried the on-line Admin Guide, but in there points out that you can only do a modified time Differential Backup if you're doing a modified time Full backup, otherwise you have to do the Back up changed files since last
full - Using archive bit (does not reset archive bit) .

Haven't tried myself yet and if that doesn't work  I'm as lost as you :(

I've copied and pasted below the text from the Admin Guide:


Differential. Includes all files that have changed since the last full or incremental
backup. The difference between differential and incremental backups is that
incremental backups include only the files that have changed since the last full or
incremental backup.
Backup Exec provides two differential backup methods, one that uses archive bit and
one that uses modified time to determine if the file was backed up. If you select to use
the Full - Back up files - Using archive bit (reset archive bit) and want to run
differential backups, you must use the Differential - Back up changed files since last
full - Using archive bit (does not reset archive bit) method. If you select to use the
Full - Back up files - Using modified time, you must use the Differential - Back up
changed files since last full - Using modified time method.
In most schemes, differential backups are recommended over incremental backups.
Differential backups allow much easier restoration of an entire device than
incremental backups since only two backups are required. Fewer required media also
decreases the risk of not being able to restore important data because of media
errors.
You should not mix differential and incremental backups together.