Forum: UltraISO
Topic: Optimize function - not optimal
started by: wixfigur
Posted by wixfigur on Sep. 18 2006,16:00
First time I´ve made a multiboot DVD, with 2 Versions of XP Pro. Most files are the same - so I use the optimize func. to save disc space.
Some files are nearly the same ( txtsetup.sif ... ), the only difference is one entry.
Ive found out, that Ultra ISO cannot differ them and copys only one of them.
Ive tried the same with Microsoft "cdimage", and checked the function "duplicate search by binary comparisons" -oc.
That worked.

Maybe thats something for the next version of Ultra ISO.

Posted by xoben on Sep. 18 2006,19:16
Thanks for your suggestion.
Posted by irso on Sep. 23 2006,01:23
What I read is that otimize function finds duplicates which actually are not duplicates.

If that is true, then it is not a suggestion, but a very serious bug, one that could lead to data loss.

Or am I reading it wrong?
Posted by xoben on Sep. 23 2006,05:44

(irso @ Sep. 23 2006,05:23)
QUOTE
What I read is that otimize function finds duplicates which actually are not duplicates.

If that is true, then it is not a suggestion, but a very serious bug, one that could lead to data loss.

Or am I reading it wrong?

Please read carefully about:
"Some files are nearly the same ( txtsetup.sif ... ), the only difference is one entry."

PS: wixfigur wants a feature for optimizing partially identical files.
Posted by irso on Sep. 23 2006,06:31

(wixfigur @ Sep. 18 2006,20:00)
QUOTE
Some files are nearly the same ( txtsetup.sif ... ), the only difference is one entry.
Ive found out, that Ultra ISO cannot differ them and copys only one of them.

Sorry, but how to understand this, then? A bit scary text, isn't it?
Posted by mwb1100 on Sep. 23 2006,09:58
I thnk the way this would work is if 2 different files have a number of blocks that are the same then those blocks might be shared between the files.

I don't know how ISO data structures are laid out, but depending on this it might be possible to optimize any blocks that are identical, or if it's laid out like similar to the FAT file system, then it might be possible to optimize only if the files have the same blocks at the end (this is because FAT filesystems have the information about which block is next contained in the block itself).
Posted by multiboot on Oct. 01 2006,00:04
I fully agree with the thread starter, UltraISO's optimizer doesn't work as precise as Microsoft's cdimage -oc. I just had to kick off some stuff from my multiboot dvd to make it fit without the optimizer, otherwise there would be errors in txtsetup.sif.
Posted by irso on Oct. 03 2006,22:49

(multiboot @ Oct. 01 2006,04:04)
QUOTE
...there would be errors in txtsetup.sif.

I think, now it should be clear that there is a bug, or at least so it is reported?