In general do the operating systems for desktops and workstations require more or less memoy than the operating systems for servers?

Answer 1

"They typically require about the same, but you will find that servers have more memory because they are used by more clients at once." This is close to the mark, but merits some clarification. Desktops typically have just one user, and so have only a handful of processes running. Most servers are used as web servers. They respond to requests for web pages by retrieving the web page's content from disk and then sending it over the internet to the requestor's machine, which is usually a desktop. The "more clients" of a server are not individual users, but "more client requests" from remote users. Also, a single remote user may launch multiple requests at the same time. For example, Google and other search engines use programs called "robots" or "Spiders" that systematically probe the internet looking for newly published content. Servers do indeed usually have more memory then desktops, and often much more of it, for a variety of reasons. Typically the server will launch a separate thread for each request. Each such thread needs memory of its own, though the amount required is much less than that needed to process each request by creating a full copy of the server code. That is, you only need to provide new memory space for the thread's data and execution state. The requests for pages are not uniformly distributed. For example, the "Slashdot effect" is the name given to the effect observed when Slashdot publishes a new story with a tantalizing title. Many Slashdot readers then click on the link, and so some server which has been quietly working away with a modest workload is suddenly faced with a torrent of requests from multiple users all seeking to access the same page at the same time. Multiple requests for the same page at the same time are also common to news sites such as cnn and the New York Times. The standard approach to deal with this is to "cache" the content, by which is meant that the content is copied from disk to memory. Memory is much faster than disk memory, usually by at least a factor of one hundred.

Desktops also need much less memory because they serve only a single user, so the demand on the processor is constrained both by the speed at which the user can type and the speed at which data can be sent over the internet. This has resulted in "server consolidation," in which many workstations are consolidated by putting the disks on a single server. For example, a large IBM mainframe can support tens of thousands of individual desktop users. This is more efficient in hardware cost and especially in the amount of electric power required.

Most desktops are busy only a tiny fraction of the time. For example, consider a typical home user running Windows on a 2GHz desktop. They may read 20 emails, view 100 pages, and write 2 or 3 emails in an evening. The load on the processor is less than a minute's worth of work, but the desktop is consuming electricity at essentially the same rate for the entire evening. For example, my Ubuntu desktop typically idles at 60 watts, and goes up to about 100 watts briefly when I accesss a web page or do a compilation. Four hours is 240 minutes, so in four hours most machines are used for only a minute, much less than one percent of the time on. thanks,dave http://daveshields.wordpress.com