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I’m frustrated

discspan doesn't do large files...

I have used nero for years but have never used the discspan feature. I have to assume this problem is unique enough that it hasn't been reported.

Problem - need to make archival copies of VMware images (500GB+)
solution: Use 7-zip to compress them to a more reasonable size (70GB+)
burn them to bluray (tried 25GB and 50GB media) using discpan.

What happened:
7-zip compressed the files and tested the resulting files as ok.
Nero burning rom (blu/ray,UDF format) with disc span enabled split the files with the only warning that a file had changed (this was impossible) and verification said it was OK.
use diskmerge to recombine the files to disk - all ok there.
use 7zip to test the extract produced from diskmerge and it reports data errors.
use 'comp.exe' to compare the source and diskspaned 7zip files and there are differences. I could be sketchy on my hex to decimal conversion but the first difference appeared at 3.4GB mark and was consecutive after that.

I repeated 3 three times on different systems: Nero 2011 and 2015 platinum versions along with different hardware and of course media and burners.

It seems like a bug to me, pretty annonying and scary because if I wasn't OCD about this the problem would have gone unnoticed.

thanks,
Bill
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  • I'm bumping this so it doesn't get lost. Not ready to respond yet.
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  • Hi Bill,

    I tried to replicate the issue reported by you and there seems to be a successful discspan and discmerge without any data errors post 7zip extract too.
    Kindly share the logs if in case the error comes up again for further analysis.

    Thanks!
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  • Since this is repeatable and nothing appears wrong in the operation, I don't know what the logs are going to offer. Besides I don't know how do this without investing hours and wasting media in the process.

    However, I realize upon reflection that I had 7-zip split the files so are all the same size. This occurred when I told 7-zip to split at 24000MB and 22g the 24option directory is listed below.

    Volume in drive G is VM_Export
    Volume Serial Number is FA81-3189

    Directory of G:\final.24g

    11/17/2017 05:45 AM .
    11/17/2017 05:45 AM ..
    11/15/2017 06:59 AM 23,111 manifest.txt
    11/01/2017 11:33 PM 24,036,739,786 oply_depot.7z
    11/15/2017 12:51 PM 25,165,824,000 vm_x2017.7z.001
    11/15/2017 12:51 PM 25,165,824,000 vm_x2017.7z.002
    11/15/2017 12:51 PM 25,165,824,000 vm_x2017.7z.003
    11/15/2017 12:51 PM 25,165,824,000 vm_x2017.7z.004
    11/15/2017 12:51 PM 25,165,824,000 vm_x2017.7z.005
    11/15/2017 12:51 PM 25,165,824,000 vm_x2017.7z.006
    11/15/2017 12:51 PM 25,165,824,000 vm_x2017.7z.007
    11/15/2017 12:51 PM 4,805,407,220 vm_x2017.7z.008
    10 File(s) 205,002,938,117 bytes
    2 Dir(s) 377,071,137,792 bytes free

    I think a 50GB burn with verification is about 2hours, so your request would be no less than 10 hours plus media costs. I think you can understand my reluctance to do this again after doing it three times before posting this issue.

    thanks,
    bill
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  • thinking further about the 7-zip construction which may affect what is in the files, the 7-zip both version 9.20 and 16.04 both created files that couldn't be discpanned/merged by Nero and in all cases the files were LZMA2 compressed with Ultra compression set, large dictionary (1024MB) and no less than 12 threads. The source files were 1.7TB in size; the directory above is of course the files that 7-zip created/verified/could export and were input to Nero.

    I appreciate you attention to this matter,
    Bill
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  • Finally, the last bit of detail I think I can offer is that I was told (somewhere) that the first data in the 7-zip file describes the archive, compression settings, etc.

    If true that information may be helpful for you to recreate a similar file.
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  • This was done on 64 bit 7-zip with lots of memory and CPU... the ones you are looking at were created using 2 - 6 core Xeon processors and 150GB of memory.

    However the 22GB version was done on a smaller system with a single Xeon processor and 48GB of memory with a smaller dictionary size which should be easier to obtain.
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  • Hi Bill,

    We are unable to reproduce the issue with the details shared by you. Will it be possible for you to share us the files that you use so that we can get to know more about the discmerge or discspan issues?

    Thanks!
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  • Unfortunately not. The biggest reason I cannot share the files is that these are VM host images which contain company data which cannot be disclosed to anyone out side the company.
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