Servers

CPTE 433John 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

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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