So for now it is up to all of the individual users to know they cannot use tar without the -P switch if they are accessing a data storage system that uses gluster?
David (Sent from mobile) =============================== David F. Robinson, Ph.D. President - Corvid Technologies 704.799.6944 x101 [office] 704.252.1310 [cell] 704.799.7974 [fax] david.robin...@corvidtec.com http://www.corvidtechnologies.com > On Dec 21, 2014, at 12:30 PM, Vijay Bellur <vbel...@redhat.com> wrote: > >> On 12/20/2014 12:09 PM, David F. Robinson wrote: >> Seems to work with "-xPf". I obviously couldn't check all of the files, >> but the two specific ones that I noted in my original email do not show >> any problems when using -P... > > This is related to the way tar extracts symbolic links by default & its > interaction with GlusterFS. In a nutshell the following steps are involved in > creation of symbolic links on the destination: > > a) Create an empty regular placeholder file with permission bits set to 0 and > the name being that of the symlink source file. > > b) Record the device, inode numbers and the mtime of the placeholder file > through stat. > > c) After the first pass of extraction is complete, there is a second pass > involved to set right symbolic links. In this phase a stat is performed on > the placeholder file. If all attributes recorded in b) are in sync with the > latest information from stat buf, only then the placeholder is unlinked and a > new symbolic link is created. If any attribute is out of sync, the unlink and > creation of symbolic link do not happen. > > In the case of replicated GlusterFS volumes, the mtimes can vary across nodes > during the creation of placeholder files. If the stat calls in steps b) and > c) land on different nodes, then there is a very good likelihood that tar > would skip creation of symbolic links and leave behind the placeholder files. > > A little more detail about this particular implementation behavior of > symlinks for tar can be found at [1]. > > To overcome this behavior, we can make use of the P switch with tar command > during extraction which will create the link file directly and not go ahead > with the above set of steps. > > Keeping timestamps in sync across the cluster will help to an extent in > preventing this situation. There are ongoing refinements in replicate's > selection of read-child which will help in addressing this problem. > > -Vijay > > [1] http://lists.debian.org/debian-user/2003/03/msg03249.html > _______________________________________________ Gluster-devel mailing list Gluster-devel@gluster.org http://www.gluster.org/mailman/listinfo/gluster-devel
