The 'gfid-access' translator provides access to data in glusterfs using a virtual path. This particular translator is designed to provide direct access to files in glusterfs using its gfid. 'GFID' is glusterfs's inode number for a file to identify it uniquely. As of now, Geo-replication is the only consumer of this translator. The changelog translator logs the 'gfid' with corresponding file operation in journals which are consumed by Geo-Replication to replicate the files using gfid-access translator very efficiently.
Implications and Usage
A new virtual directory called '.gfid' is exposed in the aux-gfid mount point when gluster volume is mounted with 'aux-gfid-mount' option. All the gfids of files are exposed in one level under the '.gfid' directory. No matter at what level the file resides, it is accessed using its gfid under this virutal directory as shown in example below. All access protocols work seemlessly, as the complexities are handled internally.
Mount glusterfs client with '-o aux-gfid-mount' as follows.
mount -t glusterfs -o aux-gfid-mount
#mount -t glusterfs -o aux-gfid-mount rhs1:master /master-aux-mnt
Get the 'gfid' of a file using normal mount or aux-gfid-mount and do some operations as follows.
getfattr -n glusterfs.gfid.string
#getfattr -n glusterfs.gfid.string /master-aux-mnt/file # file: file glusterfs.gfid.string="796d3170-0910-4853-9ff3-3ee6b1132080" #cat /master-aux-mnt/file sample data #stat /master-aux-mnt/file File: `file' Size: 12 Blocks: 1 IO Block: 131072 regular file Device: 13h/19d Inode: 11525625031905452160 Links: 1 Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Access: 2014-05-23 20:43:33.239999863 +0530 Modify: 2014-05-23 17:36:48.224999989 +0530 Change: 2014-05-23 20:44:10.081999938 +0530
Access files using virtual path as follows.
#cat /master-aux-mnt/.gfid/796d3170-0910-4853-9ff3-3ee6b1132080 sample data #stat /master-aux-mnt/.gfid/796d3170-0910-4853-9ff3-3ee6b1132080 File: `.gfid/796d3170-0910-4853-9ff3-3ee6b1132080' Size: 12 Blocks: 1 IO Block: 131072 regular file Device: 13h/19d Inode: 11525625031905452160 Links: 1 Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Access: 2014-05-23 20:43:33.239999863 +0530 Modify: 2014-05-23 17:36:48.224999989 +0530 Change: 2014-05-23 20:44:10.081999938 +0530
We can notice that 'cat' command on the 'file' using path and using virtual path displays the same data. Similarly 'stat' command on the 'file' and using virtual path with gfid gives same Inode Number confirming that its same file.
Nature of changes
This feature is introduced with 'gfid-access' translator.