Mailinglist Archive: opensuse (1700 mails)

["Brian K. White" <brian@xxxxxxxxx>]

Boyd Stephen Smith Jr. wrote:
> On Tuesday 15 September 2009 14:22:50 Carlos E. R. wrote:
>   
> > > As for tools designed to embed data to assist in recovering from or at
> > > least minimizing loss of data due to media errors, including in concert
> > > with compression:
> > > In the free world right off the top of my head, dar and xar. And dar
> > > just uses parchive which you could use seperately with something else
> > > too. And any of the official backup programs (amanda, zmanda, bru,
> > > bacula, arkeia, ...?)
> > > And basically any of the commercial programs.
> > >       
> > I wonder why not on free software.
> >     
> Amanda and Bacula are free software the last time I checked.
>   

Seems silly to quote something that is already quoted right there above
but...
"In the free world right off the top of my head, dar and xar."

Dar itself has checksumming so it can detect media errors and contain
their scope to just the affected files and not the whole archive,
including with encryption. But doesn't go as far as adding ECC data to
actually compensate and magically produce lost data.
However it works with a sepoerate add-on utility called parchive which
does exactly that. Better yet, youy can use parchive with pretty much
any other utility you want, not just dar.

xar is newer and does all that stuff within itself.

Both attempt to handle all the stuff new filesystems and new kernels
support that old file formats have no provisions for because the ideas
hadn't been thought of yet when tar and cpio were developed.

Star is a funny case where he tries to squeeze every possible bit of
functionality out of the latest tar specifications, making full use of
the allowances for vendor or future-use extensions. The fact that mostly
no one elses tar implementations does this except the commercial
"supertars" like lonetar and backupedge, isn't a problem with the file
format. I love star. I wonder if there is a neat clean way to add ECC
data within the existing framework the way star manages to handle all
the new and extended file metadata within it? If not, Well there is
always the parchive route which has really not much wrong with it that I
can see.

http://dar.linux.free.fr/doc/Features.html :
"DATA PROTECTION: dar relies on the Parchive program for data protection
against media errors."

http://parchive.sourceforge.net/ :
"Parchive: Parity Archive Volume Set
The original idea behind this project was to provide a tool to apply the
data-recovery capability concepts of RAID-like systems to the posting
and recovery of multi-part archives on Usenet."

http://code.google.com/p/xar/ :
I must have misremembered something about xar. I see nothing there about
ECC data. It certainly seems like that could be just one of many
possible uses for it's extensively extensible format, so perhaps what
I'm remembering is some discussion about that, not any actual feature
currently implimented.

-- 
bkw

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