1.3.2. Additional Differences Between GFS and GFS2
GFS2 file systems support the use of the chattr
command to set and clear the j
flag on a file or directory. Setting the +j
flag on a file enables data journaling on that file. Setting the +j
flag on a directory means "inherit jdata", which indicates that all files and directories subsequently created in that directory are journaled. Using the chattr
command is the preferred way to enable and disable data journaling on a file.
atime_quantum parameter removed
The GFS2 file system does not support the atime_quantum
tunable parameter, which can be used by the GFS file system to specify how often atime
updates occur. In its place GFS2 supports the relatime
and noatime
mount options. The relatime
mount option is recommended to achieve similar behavior to setting the atime_quantum
parameter in GFS.
The data= option of the mount command
When mounting GFS2 file systems, you can specify the data=ordered
or data=writeback
option of the mount
. When data=ordered
is set, the user data modified by a transaction is flushed to the disk before the transaction is committed to disk. This should prevent the user from seeing uninitialized blocks in a file after a crash. When data=writeback
is set, the user data is written to the disk at any time after it is dirtied. This does not provide the same consistency guarantee as ordered
mode, but it should be slightly faster for some workloads. The default is ordered
mode.
The gfs2_edit
command supports a different set of options for GFS2 than the gfs_edit
command supports for GFS. For information on the specific options each version of the command supports, see the gfs2_edit
and gfs_edit
man pages.