I've noticed that I'm using sessions quite a bit to keep track of data and plan on undertaking a project that will use even more sessions. From what I understand, when a session is created a file is also created on the server. My use of sessions involves creating them, and then unsetting them when I'm done with them; sometimes this unsetting occurs at the end of a page, sometimes soon after the session is created.
I'm concerned that all this session setting and unsetting will cause the hard drive to become heavily fragmented; especially with large amounts of traffic. Is there need for concern here or should I proceed with my project?
If there is no need to keep sessions during a server reboot, you can create a partition as an automatically sizing ramdisk with the tmpfs attribute in /etc/fstab and mount this partition at the location where you normally store your sessions. See man mount for more details.