Servers CPTE 433 John Beckett

Server Hardware Extensible More CPU performance High-performance I/O Upgrade options Rack mountable No side-access needs High-availability options Maintenance Contracts Management Options

Select Vendors for Reliability More people depend on a given server than on an individual workstation, so it matters Talk with other SAs Standardize on a vendor and product line to reduce costs –Cost of knowing how to maintain –Cost of spares –Cost of wasting components when reorganizing

Cost Cost per unit of performance will be higher for a server That cost is spread over many users The users may be local PCs, Web clients, or a combination

Maintenance Contracts & Spare Parts Non-critical: 2-day response may be OK –Development machines Groups of similar servers –Extensive spares kit Critical host: Perhaps a maint contract with same-day response –The old way of doing it Can you get vendor to store spares on-site? On-site tech

Spares How good is that spare on your shelf? –Do they go bad on the shelf? Did you re-order it when the previous one died? RMA – Return Material Authorization Cross-shipping Is that spare really bad? –Is the “new” one really good?

Data Integrity Windows insists on saving some data on the local machine –Registry entries Good reason to image UNIX machines have their own set of challenges

Servers Belong in the Data Center Proper environment –Power –UPS –HVAC High-bandwidth connections to backup Access by techs Field office: Need a server closet

Client/Server Configuration Web: No need to be the same UNIX: Often need the same –Use NFS to mount server’s resources on clients, which may be diskless –Similar situation (Citrix) available for Windows

Provide Remote Access KVM switch –Large versions work via Ethernet, which requires reliable net Remote Console UNIX: Simple Ethernet connections work fine, especially for command-line management

Mirror Boot Disks Keep a copy of the boot partition so you can get the machine up quickly if needed Include the tools needed for full recovery

Server Appliances Servers sold from the outset for specific purposes Engineered for optimal performance Pre-configured May include features you can’t get otherwise May be locked down or otherwise limited –Example: Almost any networking box at Best Buy

Redundant Power Supplies Either “hot swap” or no reason to bother Either power supply must have enough power for the system Separate power cords, plugged into separate circuits all the way to separate breakers Do you need to UPS on both sides? –Probably not, since you are guarding against different dangers –But you need to deal with down supplies quickly

Full versus n + 1 Redundancy n + 1 means you can handle any single failure Do your problems only come one at a time? Full redundancy may provide load sharing, which helps iron out peaks When using n + 1 redundancy, it is important to swap out failed components quickly before a second failure occurs –Especially important if n is a large number

Questions About Redundancy Which parts are not hot-swappable –RAID controller (often the source of problems anyhow) Hot-Plug or Hot-Swap –Hot-Plug: Nothing will be broken if you change, but you’ll probably have to reboot –Hot-Swap: The software keeps on running

Separate Network for Administrative Functions Performance problems might lock you out You can’t fix it if you can’t get to it

Alternative: Many Inexpensive Servers Identical servers that you never move to reduce failure points If you manage failures well, this could save a lot of money Recognize that failures are part of the game If the load can be balanced, this might be a very scalable architecture Disposable servers? Opposite approach: Virtualization/Clustering

Blade Servers Dell sells them if you want them Economics haven’t really panned out Go with commodity servers instead Or a cluster of large servers for virtualization

Server Connectivity

Mainframe Terminal Controller Termin al

A New World Begins Mainframe Terminal Controller Termin al Hub PC Internet

More PCs Mainframe Terminal Controller Termin al Hub PC Internet

Duh… Mainframe Terminal Controller Termin al Switch PC Internet PC

The Problem Has Moved Mainframe Terminal Controller Termin al Organized Network PC Internet PC Need Speed Here

The “Final” solution Server Organized Network PC Internet PC Need Speed Here Server

The Next Wave(s) Server Organized Network PC Internet PC Need Even More Speed Here Server Cloud Services Servers become services, and can be anywhere Everything communicates via IP and Here Sun Microsystems: “The network is the computer”

Convergence More of our corporate operations are going over the Ethernet network as time goes on. The network must be faster. –Performance is more difficult to predict. The network must be more reliable. –Failures will disable more of the organization.

Monitor Your Servers Room temperature records can tell you when people were there –And when they forgot to close the door Humidity can be an issue Security camera image capture? –Digital security camera systems are far better than analog

Server Proliferation If you implement a server for each application, you’ll end up with an awful lot of servers –Disadvantages: Heat/Power, Support cost Current approach is to virtualize: –Super-server that is large and super-reliable Perhaps clustered –Consistent implementation of servers within that hardware server –Control software that allows easy manipulation of virtual servers: Creating backup images Migrating from one hardware server to another