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Backup Size Compared To Original


MikeGiann

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Hi All,

 

Don't know if this has been answered already, but I did a search and found nothing for my query. I would like to know if it's normal or not, I'm using Retrospect 6.0 Pro on Windows XP Home and I'm trying to backup my data in My Documents folder. The problem is that my backup is bigger than my source data that I'm trying to backup. An example is in My Documents I have a folder called Software Updates and uncompressed it is 958.0 MB but the Retrospect backup on my 2nd hard drive is 1.4 GB. Another folder in My Documents is 4.6 GB and the Retrospect backup is 5.59 GB.

I verified the settings and removed all ckeckmarks for backing up system state, outlook folders, ect. I only want what is in the folder to be backed up. I don't have a license for the open files backup so that can't be it either.

Can anyone help as to what I'm doing wrong? I'm pretty sure that the backup shouldn't be larger than what the source data is. Right?

Thanks for any help.

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Hi

 

This is actually a pretty common question.

 

Retrospect backups add new and changed files to your backup set. It also maintains a history of how your disk looked every time you back up. As a result the backup set will continually grow in size.

 

To start the backup from scratch again run a "recycle backup". The contents of the set will be erased and all of your files will be backed up again.

 

Nate

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Hi Nate, thanks for helping me out. Retrospect does this with a new installation and a new backup set. When creating a new backup set and specifying the folders to backup and it performs it's first initial backup, it's already larger than the folder where the data is on.

I did notice that in my backup set, I had chosen backup to disk, which is what is larger than the source data. However if I chose the backup to file, then it is smaller than the source, because of the compression. This is what I would like, but how come if I choose backup to disk the size of the backup increases? Is this normal? I would like to choose backup to disk because it puts the files in sizes of 650 mg which i then can put on cd's. Backup to file creates one huge file.

Again thanks for all your help.

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Quote:

MikeGiann said:

 

Hi Nate, thanks for helping me out. Retrospect does this with a new installation and a new backup set. When creating a new backup set and specifying the folders to backup and it performs it's first initial backup, it's already larger than the folder where the data is on.

 

I did notice that in my backup set, I had chosen backup to disk, which is what is larger than the source data. However if I chose the backup to file, then it is smaller than the source, because of the compression. This is what I would like, but how come if I choose backup to disk the size of the backup increases? Is this normal? I would like to choose backup to disk because it puts the files in sizes of 650 mg which i then can put on cd's. Backup to file creates one huge file.

 

Again thanks for all your help.

 


 

 

 

 

 

It is possible, perhaps unlikely, that your files are of the type that increase in size when compressed by whatever compression algorithm Retrospect is using.

 

 

 

Another issaie is is this a File backup set or a Disk backup set?

 

A disk backup sert writes the catalog to a separate set of files.

 

 

 

A File backup set, as I understand it, places the catalog in the backup set itself, thus increasing the apparent size of the backup set. If forced to guess, I'd guess that this what you are seeing.

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Hi Howard and a big thanks. That seems to have solved my problem, all I did was remove the compress in software and the file size is identicle to the source data's folder. Now I'm just wondering why with software compression does the size increase instead of decrease silightly. I mean if the files are already compressed then it should do nothing and I'm pretty sure that there is always something that can be compressed slightly, even if it's only a few bytes. Oh well, at least now the backups won't take up more space then the original folder.

To answer your question this was a disk backup set, that is why I was confused as to the larger size. In the file backup, the catalogue files are integrated with the backup and that I would understand that it would be larger (but not by double the size!!)

Now I guess I just have to leave the compression off. I have the 6.0 pro version, I wonder if the 6.5 has a better compression algorithm than the 6.0 and will only compress what can be compressed. I wouldn't want to purchase the upgrade and have the same thing happen again.

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There are a number of compression algorithms that may be used by hardware/software.

 

 

 

Some algorithms can cause an increase in the file size, especially if the file has already been compressed by particular algorithms.

 

 

 

It's in the mathematics of the algorithms, and does depend on the particular date being compressed. I haven't looked at the subject in a few years, so I do not recall all the details.

 

 

 

Are you doing hardware compression, as well as software compression?

 

 

 

I back up to an NTFS volume, but I've got NTFS compression disabled.

 

Dunno what would happen if I enabled NTFS compression.

 

Could that be the problem?

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Hi, I too am backing up to a NTFS volume but I do believe that the NTFS compression is off. When I right click on all of my drives and in the Properties section at the bottom where it says "compress volume to save space" it is not checked.

I was only using the software compression that is in Retrospect and it caused the backups to be much greater than the source data. Since I removed the software compression in Retrospect, all the backups seem to be about the same size as the source data.

 

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Here's a demonstration of compression increasing a file's size:

 

1. Create a text file consisting of the 26 lletters of the Latin alphabet as a single string.

File size is 26. Let's call this letters.txt.

 

2. Now, using your favorite program, create a .zip for that file. In my case, using defaiult options, the size of the .zip file is 146.

 

3. OK, now make a copy of letters.txt and name the copy 16letters.txt. In letters.txt create 16 lines, each consisting of the 26 letters of the Latin alphabet. File size is now 446.

 

4. Now create a .zip of 16letters.txt. In my case, using default options, the size of the .zip fie is 159 bytes.

 

5. Now, let's get adventuresome.

 

You now have 16letters.zip, a highly compressed file of 159 bytes.

So; let's get greedy, let's try zipping the 16letters.zip file.

Doing so, using default options, I find the the .zip of the .zip has 243 bytes.

 

 

Why does this occur?

 

Because the algorithm used by the zip program cannot compress letters.txt, but can do quite good compression of 16letters.txt.

 

Ditto for 16letters.zip.

 

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