Re: [Bug-tar] use optimal file system block size

[Ralph Corderoy]

Hi Christian,

> $ stat -c %o data/blob
> 2097152
...
> **tar** does not explicitly use the block size of the file system
> where the files are located, but, for a reason I don't know (feel free
> to educate me), 10 KiB:

Historic, that being 20 blocks where a block is 512 B.  See `Blocking
Factor'.  https://www.gnu.org/software/tar/manual/tar.html#SEC160

It can be changed.

    $ strace -e write -s 10 tar cbf 4096 foo.tar foo
    write(3, "foo\0\0\0\0\0\0\0"..., 2097152) = 2097152
    +++ exited with 0 +++
    $

> I would like to propose to use the native file system block size in
> favor of the currently used 10 KiB.

I can't see the default changing.  POSIX's pax(1) states for ustar
format that the default for character devices is 10 KiB, and allows for
multiples of 512 up to an including 32,256.  So you're suggesting the
default is to produce an incompatible tar file.

-- 
Cheers, Ralph.
https://plus.google.com/+RalphCorderoy