prohibited entirely (if the image is a network filesystem). This allows use in public access areas (such as libraries) or in schools etc., where users might wish to experiment or attempt to "hack" the system. However, it is not necessary to implement network booting to achieve either of the above advantages - ordinary PCs (with the help of appropriate software) can be configured to download and reinstall their operating systems on (e.g.) a nightly basis, with extra work compared to using shared disk image that diskless nodes boot off. Modern diskless nodes can share the very same disk image, using a 1:N relationship (1 disk image used simultaneously by N diskless nodes). This makes it very easy to install and maintain software applications: The administrator needs to install or maintain the application only once, and the clients can get the new application as soon as they boot off the updated image. Disk image sharing is made possible because they use the write cache: No client competes for any writing in a shared disk image, because each client writes to its own cache. All the modern diskless nodes systems can also use a 1:1 Client-to-DiskImage relationship, where one client "owns" one disk image and writes directly into said disk image. No write cache is used then. Making a modification in a shared disk image is usually made this way: The administrator makes a copy of the shared disk image that he/she wants to update (this can be done easily because the disk image file is opened only for reading) The administrator boots a diskless node in 1:1 mode (unshared mode) from the copy of the disk image he/she just made The administrator makes any modification to the disk image (for instance install a new software application, apply patches or hotfixes) The administrator shutdowns the diskless node that was using the disk image in 1:1 mode The administrator shares the modified disk image The diskless nodes use the shared disk image (1:N) as soon as they are rebooted. Centralized storage The use of central disk storage also makes more efficient use of disk storage. This can cut storage costs, freeing up capital to invest in more reliable, modern storage technologies, such as RAID arrays which support redundant operation, and storage area networks which allow hot-adding of storage without any interruption. Further, it means that losses of disk drives to mechanical or electrical