[lbackup-discussion] Time point backup schema?

[Daniel.Li]

On Thu, 2009-03-12 at 08:29 +1300, henri wrote:
> 
> 
> .... cut ......

> > e.g. If I have a single file with the size of 10MB(for backup test
> > only).
> > I have slightly change one byte or one bit data at end of the file.  
> > How
> > much disk space will LBackup take for the next snapshot?
> >
> > As u know, rsync just backup file to latest version, which will  
> > consumes
> > one byte/bit of the diskspace. Of cause, it does NOT have a snapshot
> > feature.
> >
> > Now, we just lower the network requirement with rsync, which is ideal
> > for mirroring. So back to LBackup, how much space will LBackup takes
> > with the next snapshot, which is a key point to disk management.
> >
> .... cut ......
> 
> 
> Because two separate versions of the file will exist in the file  
> system and they will not be hard linked, the old copy will consume  
> 10MB and the new copy will consume an additional 10MB + 1 byte/bit.  
> This means that in total storage required for these two snapshots will  
> be 20MB + 1 byte/bit.
> 
> LBackup currently has no support for this kind of delta backup/copy.  
> There are other backup tools available if this is a feature which you  
> require.

Actually, I hope that I can find some software, including this feature. 
Well, apparently, I didn't found any. So I think I need a basic backup, l
ike LBackup system, which uses hard link to reduce the size of snapshots.

> 
> I am interested to know if some sort of delta copy is possible,  
> perhaps though some sort of file system trickery or in some other way.  
> This would be a great feature and under certain circumstances it would  
> greatly reduce the required backup storage capacity. If I find someway  
> to do this or if you know of some way to do this then that is  
> definitely a feature to look at incorporating into the project.

Humm.... I think this is great feature can downsize the backup storage dramatically,
especially on media applications.

Well, I have a very simple plan, which might be work, but I haven't check how much work that we need to do.

Binary patches schema:
Maybe we can pull out some core algorithm used in rsync, any do the binary differs, and arrange these differs like git tool.

If it's possible, then we might solve the issue. What do u think? :)

> 
> As it stands this kind of delta copy is not supported by LBackup even  
> though this feature will in certain circumstances dramatically  
> increase the storage requirements for the backup.

I have checked EMC's software, and I didn't found binary diff schema also.

Anyway, if it needs long time to accomplish. Maybe it should do opensource, which I can do some program out of work.
Also, currenly, we have plan to accomplish a basic backup tool for our Nas product.


And I also don't have any idea about how much time we need to get LBackup work on windows platform. Do u have any ideas? 

Cause in this financial crisis, we are in a hurry. :(

> 
> Thank you for this great question!
> 
> I will add this feature request to the developer section of the  
> LBackup site : http://connect.homeunix.com/lbackup/developer/
> 
> Thank you again.
> 
> 
> PS : This message made it to the list just fine. Your assistance is  
> greatly appreciated!

Yeah, It seems work well with my public mailbox. 
I'll check it with our IT engineer today:)

They changed my mail server. try it again.

Thanks for ur help.
> 
> 
> 
> 
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