All the professional filesystems store at least three type of date for each file. These are file creation time, last modified time and the last accessed time.
File’s last accessed time changes very frequently, even a directory listing operation leads to change all of the files’ last accessed time information under that directory.
So, this will introduce a filesystem overhead. If you don’t need to exact last accessed time of files under specific mount point, you can disable this future with the noatime mount option. to do this, edit /etc/fstab and add noatime option in the option group field like below:
/dev/sda7 /var ext3 defaults,noatime 0 0
In order to take effects immediately, you can remount this partition with:
mount -o remount /var
This change can improve the overall filesystem performance in a heavy loaded web server or database system.