Re: [Bug-tar] Issue with GNU Tar and HP-UX LVM v2.2 filesystems

[Nathan Stratton Treadway]

On Fri, Sep 28, 2012 at 20:22:20 +0000, Michael White wrote:
> I think maybe I've confused the issue by talking about VG's and LVM. 
> But HP's LVM version 2.2 for sure has changed the way it writes
> metadata on the files which is breaking GNU tar's incremental
> operation.  I think that's evident by the tar-snapshot-edit utility
> check of the field values of the snapshot file.  When it hits a
> filesystem that has been initialized as a HP LVM 2.2.  I get the " Dev
> value too high" error otherwise I don't get the error.
> eg:                Dev value too high: "18446744071562076161" > 4294967295
> 

The point is that GNU tar doesn't know that the files you are trying to
back up are on an LVM volume, and thus doesn't do any special processing
like trying to look up LVM metadata for them.

Essentially, all tar does is request the "stat" information from the OS
for each file and directory it's processing, and then uses the device id
(and lots of other fields) taken out of that information.

So it sounds like then HP/UX LVM 2.2 is used, the device id that gets
assigned to a volume is unusual in some way that causes trouble for
tar... but the issue ties back to the values returned by the standard
"stat" function call, and not to some attempt by tar to parse the LVM
metadata or whatever.

(It's possible that the device id assigned to an LVM volume is somehow
related so some information stored in the metadata, but if that's the
situation it's happening within HP/UX somewhere, not within GNU tar.)

So, if you can find some way to print out "directly" the device id value
returned by the stat call, that could shed some light on why the value
in question is causing problems for tar.


> But the tar-snapshot-edit utility calls out every file and directory
> like above as well if the filesystem was initialized as a HP LVM 2.2

Yes, by definition all files and directories on a particular filesystem
have the same device id, so you'd expect the same error to happen for
the snapshot file entries for all those objects.



> Would it help any if you saw the snapfile?

(It won't help for me to see it, though perhaps one of the tar
maintainers will want to look at at some point.)
 
> On additional note, do you know who has been porting GNU tar to The
> Porting And Archive Centre for HP-UX in the United Kingdom?  This

(No, sorry, I don't know anything about that side of things; hopefully
someone else on the list will have an answer for you...)


                                                        Nathan
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