On 17/11/14 14:36, Klaus-Jürgen Wolf wrote: > I have to correct my former comment: cp --sparse=never only works with very > small files, e.g. 542 bytes. > > (PWD=/home/kj/MyDrive) > > $ /bin/cp --sparse=never ~/prj/kaese/cpp/Makefile . > $ stat Makefile > File: ‘Makefile’ > Size: 542 Blocks: 2 IO Block: 4096 regular file > Device: 28h/40d Inode: 18825536 Links: 1 > Access: (0644/-rw-r--r--) Uid: ( 1000/ kj) Gid: ( 1000/ kj) > Access: 2014-11-17 15:27:05.000000000 +0100 > Modify: 2014-11-17 15:27:05.000000000 +0100 > Change: 2014-11-17 15:27:05.000000000 +0100 > Birth: - > > $ dd if=/dev/zero conv=notrunc count=1 seek=1 of=/home/kj/MyDrive/eio.test > 1+0 records in > 1+0 records out > 512 bytes (512 B) copied, 0.00248944 s, 206 kB/s > > But, with longer files: > > $ /bin/cp --sparse=never ~/Tc7200.bin . > /bin/cp: error writing ‘./Tc7200.bin’: Input/output error > /bin/cp: failed to extend ‘./Tc7200.bin’: Input/output error > > $ ll ~/Tc7200.bin > -rw-r--r-- 1 kj kj 26296 Sep 8 21:45 /home/kj/Tc7200.bin > > I need to say that using tar, I can produce much longer files: > > $ stat kaese20141116.7z > File: ‘kaese20141116.7z’ > Size: 981305 Blocks: 1917 IO Block: 4096 regular file > Device: 28h/40d Inode: 18802464 Links: 1 > Access: (0644/-rw-r--r--) Uid: ( 1000/ kj) Gid: ( 1000/ kj) > Access: 2014-11-16 11:13:20.000000000 +0100 > Modify: 2014-11-16 11:12:48.000000000 +0100 > Change: 2014-11-16 11:12:55.000000000 +0100 > Birth: - >
With --sparse=never we really should only be doing write()s to the destination. That could be confirmed with: strace cp --sparse=never ~/Tc7200.bin . The only thing left that I can think of is the size of the writes is causing a problem. cp will read and write 64KiB by default. tar may be using smaller than this and so not triggering the issue? I searched for that issue and noticed this fuse issue: http://thread.gmane.org/gmane.comp.file-systems.fuse.devel/14095 thanks, Pádraig.
