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#Gfid-access Translator
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.
###Testing
1. Mount glusterfs client with '-o aux-gfid-mount' as follows.
mount -t glusterfs -o aux-gfid-mount <node-ip>:<volname> <mountpoint>
Example:
#mount -t glusterfs -o aux-gfid-mount rhs1:master /master-aux-mnt
2. Get the 'gfid' of a file using normal mount or aux-gfid-mount and do some
operations as follows.
getfattr -n glusterfs.gfid.string <file>
Example:
#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
3. Access files using virtual path as follows.
/mountpoint/.gfid/<actual-canonical-gfid-of-the-file\>'
Example:
#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.
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