[arch-general] Maximum JFS file (not filesytem) size

[Anders Bergh]

On Tue, Sep 8, 2009 at 05:49, Dwight Schauer<dschauer at gmail.com> wrote:
> Dear fellow Archers,
>
> I tarred up a couple filesystems and piped the tar stream through ssh
> to a remote computer where I dd'ed it to a file. This a common backup
> method I've been using for a few years now if I'm going to wipe a
> system and start over.
>
> I'm using JFS on the arch linux system that was being copied to.
>
> The resulting file ended up being 137G (which is about right based on
> the source filesystem usage).
>
> du --human --total a4b4.tar
> 137G    a4b4.tar
> 137G    total
>
> However, I can only restore from 63G of the tar ball, so I attempted
> to see how much could be read.
>
> dd if=a4b4.tar of=/dev/null
> dd: reading `a4b4.tar': Input/output error
> 123166576+0 records in
> 123166576+0 records out
> 63061286912 bytes (63 GB) copied, 1193.69 s, 52.8 MB/s
>
> There were no critical files in that tar ball that are not kept
> elsewhere, that is not the issue. At this point I can consider what is
> past the 63G point in the tarball to unrecoverable, which is fine.
>
> I tried skipping the first 63GB, but that does not work.
>
> dd if=a4b4.tar skip=123166576 of=/dev/null
> dd: reading `a4b4.tar': Input/output error
> 0+0 records in
> 0+0 records out
> 0 bytes (0 B) copied, 27.2438 s, 0.0 kB/s
>
> It seems like it took a while to figure out that it could not perform
> this operation.
>
> The box in question is running an OpenVZ patched 2.6.27 kernel, but
> that might not have anything to do with it.
>
> Yeah, I know, I could have used bzip and made 2 separate files, I
> could have used rsync -av, I could have checked tarball before wiping
> the source files systems, etc, that is not the point here. Now that I
> know that JFS on my setup has a 63GB file size limit, I know now to
> accommodate for that in the future.
>
> I'm mainly just curious on how the system could write a larger file
> than it can read.
>
> Dwight
>

I just checked, and the max file size in JFS is 4 petabytes. Seems
like you have another problem.

-- 
Anders Bergh