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[Tueur]

Greetings,

I have had my DNS323 for a while and I have a number of questions which I haven't yet found an answer too. Ill put each one in a separate thread. So here we go...

I use my 323 as my main file storage location. My desktop and 323 are both connected to my router via CAT5 so My desktop holds literally my OS and Software. My laptops both have a wireless connection and I keep files on the laptop and sync them with the 323.

I hold my master files on the 323 and want to use an incremental backup to backup my data from the DNS to my Desktop HD However the incremental backups dont work; only the full backups do anything. I have been using Cobian for this. Can anyone make any suggestions as to how I can make this work?

Many Thanks

[fordem]

I don't know that you can make it work.

It's a well known issue caused by incompatabilities in how Microsoft's operating systems & linux handle data.

Traditionally Microsoft has used a flag, known as the archive bit, to know when a file needs to be backed up.

Here's how it works ...

We are going to assume that this is your first backup, so you're going to do a full backup and that you have three data files.  In this case, the backup utility will backup all the files and clear or reset the archive bit on all three files when it backs the file up, indicating that the file has been backed up.

For the purpose of this discussion, you now edit the first file, but do not touch the other two - whatever application you use to edit the file will set the archive bit, indicating that the file has been altered since it's last backup.  If you now run an incremental backup, the backup utility will check the archive bits on all three files, and see that only one is set, so it backs up that one file, and clears the archive bit.

There is a third method of backup - the differential backup - which looks for the archive bit, backs the file up, but does not reset the bit.

To recap ...

 - a full backup does not check for the archive bit, but backs up all the files and resets or clears the archive bit.
 - an incremental backup checks for the archive bit, backs up only files with the archive bit set, and then clears the archive bit.
 - a differential backup checks for the archive bit, backs only files with the archive bit set, and does not clear or reset the archive bit.

Works beautifully - in a pure Microsoft environment.

Let's now introduce linux, the OS used on the DNS-323 - it has no archive bit - it uses time & date stamps to know when last a file was accessed and must compare the last access to the last backup to know if the file needs to be backed up.

In the absence of the archive bit, your "microsoft" backup utility doesn't know which files need to be backed up for an incremental or differential backup, so only a full backup works.

You can TRY setting "map archive" to ON - it's in the DNS-323 Advanced/Network Settings menu - but there is no guarantee that it will work - what you really need is a backup utility that runs on a Microsoft OS and knows how to deal with linux file attributes, if such a utility exists.

Here's some reading

http://www.faqs.org/docs/samba/ch08.html

[JoeNAS]

Dear Tueur and Fordem,

Using the Archive-bit in Windows is ... uhm ... tricky, even in a pure Windows environment. I do my backups from PC's to DNS-323's (yes, all plurals) using the good-old DOS-command XCOPY. Should work the other way round too, from NAS to PC. It goes
XCOPY sourcefiles destinationdirectory /S/C/H/R/K/O/Y
for the first full backup; add a /D at the end for incremental backups. Do all this in a command prompt or a batch file. You can see all options when typing XCOPY /? as command.

BTW, it is not an really professional backup which deletes files in the backup if I delete them on my PC, there are no multiple versions and so on. But it works, with the great (for me) PLUS of having a fully identical folder-and-file structure in my backup, in which I can access each individual file from my PC's.

Good luck - and BTW2, I think that the DNS-323 is a nice thing with very good value for money (I have 3 of 'm).

Jan

[dosborne]

Although considerably slower, it is possible to use software that compares date/time stamps and/or CRC values to determine what is 'new' for incremental backups.

[Tueur]

Great replies here! Thank you very much.

So that is what the archive checkbox means on the properties screen.

Do you have any recomendations on software that compares using date stamps?

[cable2]

Hi, I have used a program (free) called "SYNCBACK" recommended by one of the moderators. http://www.2brightsparks.com/freeware/index.html
You might want to check it out.  Good luck

[Steve Pitts]

Do you have any recomendations on software that compares using date stamps?

You mentioned using Cobian Backup and I think you'll find that it has that capability. I use v9 (Amanita) and on the General tab of a backup task you will find a 'Use file attributes logic' tick box. When that option is 'ticked' then Cobian compares timestamps rather than using the archive attribute.

[Tueur]

Ill check both those out. Thank you!

[Tueur]

You mentioned using Cobian Backup and I think you'll find that it has that capability. I use v9 (Amanita) and on the General tab of a backup task you will find a 'Use file attributes logic' tick box. When that option is 'ticked' then Cobian compares timestamps rather than using the archive attribute.

Hi im using v10. unfortunately this doesnt work with incremenal backups, only full

Syncback also does not support incremental back ups with the free version.

On investigation Cobians logic for timestamp backups is pretty poor. They seem to be saying that it compares the timesamp of the file in the latest backup with the time stamp on the live file and that because an incremental backup does not contain all files the comparrison cant be made. This is daft. Simply build a table with file path and date of last backup then compare the timestamp on the live file to the date in the table... seems simple to me

[JavaLawyer]

Hi im using v10. unfortunately this doesnt work with incremenal backups, only full

Syncback also does not support incremental back ups with the free version.

Are you sure about that? I've been using the free version of Syncback for seven years (and running) strictly for incremental backup, and have been upgrading along the way.