About CRC Errors

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inpheaux
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About CRC Errors

Post by inpheaux » January 16th, 2010, 4:20 pm

There have been a lot of questions lately about CRC errors, so rather than having 50 different threads about CRC errors, here's one great big thread.

A CRC error means some of your files didn't survive the long and arduous journey across the internet. Usenet has a rather sophisticated recovery system with Par2, but Par2 still needs a good amount of data to repair files, and even Par2 is fallible. I've only come across three ways to end up with CRC errors in SABnzbd 0.5:

1) You have "Post-Process Only Verified Jobs" turned off, and your host is missing more parts than we can repair. The rar set ends up incomplete, but we'll still try to unrar it for you. Solution: Turn on "Post-Process Only Verified Jobs" and get a better news host. (Astraweb is a likely source of these errors right now.)

2) You are on Linux and are using your distro's equivalent of unrar-free instead of unrar. The "free" version of unrar is notorious for screwing up even the simplest actions. Solution: uninstall unrar-free and install unrar, either from your distro's repository or directly from RARLAB. SABnzbd conveniently warns you of this issue now.

3) The post itself is screwed up as posted to Usenet, and either there aren't enough pars to repair or the pars were also generated using a broken rar set. Solution: Download something else.

It's almost always #1, sometimes #2, and rarely #3.

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shypike
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Re: About CRC Errors

Post by shypike » January 16th, 2010, 4:50 pm

4) Bad RAM modules

Both par2 and unrar uncover bad RAM modules very effectively.

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inpheaux
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Re: About CRC Errors

Post by inpheaux » January 16th, 2010, 5:14 pm

shypike wrote: 4) Bad RAM modules

Both par2 and unrar uncover bad RAM modules very effectively.
Where would you rank this as far as rarity compared to the other three? Also, how should we have people verify, memtest86?
Last edited by inpheaux on January 16th, 2010, 7:11 pm, edited 1 time in total.

dalek
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Re: About CRC Errors

Post by dalek » January 16th, 2010, 8:34 pm

Regarding 3), rar files can be repair with rar r (unrar won't help in this case as the rar file is reconstructed). Files with CRC errors will likely be lost.

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inpheaux
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Re: About CRC Errors

Post by inpheaux » January 16th, 2010, 8:38 pm

dalek wrote: Regarding 3), rar files can be repair with rar r (unrar won't help in this case as the rar file is reconstructed). Files with CRC errors will likely be lost.
I have never personally seen this actually work, but it's a valid last-ditch effort.

gnaget
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Re: About CRC Errors

Post by gnaget » January 30th, 2010, 12:08 pm

wow, I just left astraweb for usenetserver last night, and I haven't had anymore CRC errors.  I went from 25% - 50% failure rate to 0% (at least in the short term)

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Re: About CRC Errors

Post by toker » February 19th, 2010, 12:21 pm

Hi All

I too have been experiencing the same issue.  I have tried the above 3 items that could cause sabnzbd to produce CRC errors.

I have checked my PA2 and UNRAR apps / version..
par2cmdline version 0.4
UNRAR 3.90 beta 2 freeware

I am running 0.4.12 on Ubuntu 9.10 x64, also tried 0.5.0RC6.  I think this is Ubuntu issue as the same nzb will download fine on Windows and OSX using the same USENET server.

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inpheaux
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Re: About CRC Errors

Post by inpheaux » February 19th, 2010, 12:42 pm

When you test the NZB elsewhere, are you testing it on the same hardware, different OS?

If it's different hardware, then you're likely seeing failure due to bad ram. Try running MemTest.

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Re: About CRC Errors

Post by toker » February 19th, 2010, 1:15 pm

Both - same hardware with different OS and on my laptop which is a Macbook.

I originally had Windows 7 on my AsRock Netop PC running sabnzbd 0.4.12 - no issues.

I recently reformated my AsRock to run Ubuntu x64 as I did not feel the need to purchase a Windows licence as Linux could do everything I needed.

I have tried to 0.4.12 and 0.5.0RC6 on Ubuntu x64, no joy.  If I download the extra PAR2 files (which sabnzbd should download but dont for some reason) the PAR2 repairs fine and the UNRAR is also fine.

I have tried old and new nzbs, only a few nzbs I have tried has successfully extracted.  A repair and extract via sabnzbd has not yet worked.
Last edited by toker on February 19th, 2010, 5:41 pm, edited 1 time in total.

toker
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Re: About CRC Errors

Post by toker » February 20th, 2010, 9:47 am

OK went back to Ubuntu 9.10 x86 and SABnzbd 0.4.12.  No more CRC errors.

dvdcassie
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Errors

Post by dvdcassie » February 21st, 2010, 6:06 am

Good morning,

I have also a problem for a few days, i hope somebody can help, because i am not very technical about the config.

The errors my SABNZB gives is:

Stage Par2
[PAR-INFO] 1521_scandal_flinke.vent: => Error "[Errno 12] Cannot allocate memory" while running par2_repair  ???

Stage Unrar
[RAR-INFO] 1521_scandal_flinke.vent: => Error "[Errno 12] Cannot allocate memory" while running rar_unpack  ???

whats the problem with my SABNZB 0.4.6 whitch is installed on my seedbox/server?

thanks for your help, i hope

wfrg CS ;)

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shypike
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Re: Errors

Post by shypike » February 21st, 2010, 12:37 pm

dvdcassie wrote: Stage Par2
[PAR-INFO] 1521_scandal_flinke.vent: => Error "[Errno 12] Cannot allocate memory" while running par2_repair  ???
The Operating System says you don't have enough memory.
Could because SABnzbd is using lots of it, but the OS should start swapping.

dvdcassie
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Re: About CRC Errors

Post by dvdcassie » February 21st, 2010, 2:01 pm

So what can i do about this?

regards

dvdcassie
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Re: About CRC Errors

Post by dvdcassie » February 22nd, 2010, 2:43 pm

Hallo,

is opgelost

bedankt

gr CS

SSelmer
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Re: About CRC Errors

Post by SSelmer » March 1st, 2010, 11:42 am

I've had interesting results with unpar'ing on my Linux and Mac DL-boxes (this has happened with multiple DVDs from a particular poster/show)..

In a file-set of n files there are two incompletes.
par2 identifies four(!) bad ones and repaired them, basically un-repairing two files that were never bad in the first place, sending them to unrar which fails miserably with a big CRC-error.

My solution was to just delete the "repaired" files, rename the .1 files to .rar, unpar the files again (manually, using UnRARX on my Mac) and it would magically repair the two bad files and leave all the others alone (as it should have to begin with).
Last edited by SSelmer on March 1st, 2010, 11:45 am, edited 1 time in total.
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