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The Perfect Server

The Perfect Server. Chapter 19. Contents. Explain methods and hardware used for protecting data Describe server-specific hardware for boosting speed Explain methods and hardware used for server reliability. Concepts. Networked PCs. A networked PC has four functions

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The Perfect Server

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  1. The Perfect Server Chapter 19

  2. Contents • Explain methods and hardware used for protecting data • Describe server-specific hardware for boosting speed • Explain methods and hardware used for server reliability

  3. Concepts

  4. Networked PCs • A networked PC has four functions • Must connect to a network • Data protection: if it shares data, it needs to protect the data by creating more than one copy of the data • Speed: if it shares data, it needs specialized hardware to allow it to share the data as quickly as possible • Reliability

  5. Servers and Workstations • Networked computers fall into two main classes • Servers that share resources • Workstations that access a server’s resources but do not share resources themselves • Hardware requirements differ Network server

  6. Servers and Workstations • There is nothing that says that a server needs to provide data protection, reliability, and speed – if you’re willing to live without it • Such as in a workgroup of peer-to-peer machines

  7. Protection of Data – Fault Tolerance

  8. Protecting Data • Data is a business’s most valuable resource • Business have gone out of business due to data loss • Backing up the data is a necessary function but does not fully protect the data • Backups get out of date and it takes time to restore the data • If a hard drive fails there needs to be a way to bring the data back instantly or at least very quickly

  9. Fault Tolerance • Fault tolerance is the ability of a server to respond to a hardware failure while continuing to operate

  10. Providing Fault Tolerance • Drive mirroring is when a hard drive controller reads and writes the same data to two different drives at the same time • One drive is the primary drive • The other drive is the mirror drive

  11. Providing Fault Tolerance • Drive duplexing is when you use separate hard drive controllers for each hard drive when mirroring data • If one controller goes down, the other hard drive is still accessible • Drive duplexing is also faster than drive mirroring

  12. Disk Striping • Disk striping spreads the data among multiple drives • Provides speed but if any drive fails, all data is lost

  13. Disk Striping with Parity • Disk striping with parity protects data • An extra parity drive is added that contains information to rebuild the data if one of the data drives fail • Requires at least 3 drives • If one drive fails, data may be recovered • If more than one drive fails, data is lost

  14. RAID • The different techniques of using multiple drives for data protection and speed are defined in various levels of Redundant Array of Inexpensive (or Independent) Disks (RAID)

  15. Hard Drive Technologies • Parallel Advanced Technology Attachment (PATA) is the most popular • Allows up to four drives • Uses a 40-pin ribbon cable that contains 40 or 80 wires

  16. Disadvantages of PATA • Flat ribbon cables impede air flow • Limited length of 18 inches • Can’t hot-swap PATA drives • Has reached its limits on throughput

  17. SATA • Serial ATA (SATA) creates a point-to-point connection between the SATA device and the controller • Since data is sent serially, only seven wires are needed, making the cable thinner • Maximum cable length is 39.4 inches • Hot-swappable • Much faster than PATA at 150 MBps to 600 MBps • Works well with RAID

  18. SATA Connections

  19. SCSI • Small Computer System Interface (SCSI) is a method of connecting hard drives, but is not really a hard drive technology • SCSI is a mini-network that connects devices • Uses a host adapter • Devices are daisy-chained together into a SCSI Chain

  20. SCSI Chains • Each SCSI device on the SCSI chain needs a unique SCSI ID • SCSI devices may be internal or external

  21. Internal Connections 50-pin ribbon cable or a 68-pin ribbon cable External Connections 50-pin Centronics (rare), 50-pin high density DB, or a DB-25 connector SCSI Connections

  22. RAID Implementation • RAID may be implemented using any of the hard drive technologies • RAID may be implemented using software that is part of the operating system • Provided with Windows NT Server, 2000 Server, and Server 2003 • RAID is usually implemented using hardware – special RAID controllers • RAID shows up as a single hard drive • Provides speed and data redundancy

  23. RAID Disk Management

  24. Hot-Swapping • Most RAID implementations use hardware and SCSI • Provides the ability to hot-swap failed devices without powering off or rebooting the server

  25. Implementing RAID • Some suggestions when implementing RAID are • Place the OS on a non-RAID partition or on a mirrored partition • Place swap files and temporary files on non-RAID drives • Put all of the data on their own RAID 5 array

  26. Network Attached Storage • Network Attached Storage (NAS) is a pre-built system that only does file sharing • A NAS server is optimized for file sharing • No monitor, keyboard, or mouse • Configuration is done from another system or web interface • Usually runs Linux using NFS or Samba

  27. Storage Area Network • Storage Area Networks (SANs) is a group of computers connected to an array of hard drives using an advanced serial technology such as SCSI fibre channel

  28. SANs • SANs make the array of hard disks look like one huge hard drive • Partitions may use RAID or Just a Bunch of Disks (JBOD) • May use over 100 drives • Very expensive

  29. Tape Backup • RAID provides data redundancy, but can still fail • That’s when a tape backup saves the day • Most backups are done using tape cartridges • There are three major tape backup groups • QIC/Travan • DAT • DLT

  30. QIC • Quarter-Inch Tape (QIC) is an older standard that is only used in small networks • Capacities began at 40 MB and reach up to 8 GB • Currently in use in Travan format

  31. DAT • Digital Audio Tape (DAT) uses a digital recording method • Stores up to 24 GB • Popular for medium-sized networks • Uses a SCSI connection

  32. DLT • Digital Linear Tape (DLT) is a new standard • Stores up to 70 GB • Very fast and reliable • Uses a SCSI connection • Expensive

  33. Speed

  34. The Need for Speed • When a computer shares resources, its performance will slow down • There are a number of issues that come into play to maintain a fast server • Multiple CPUs and more RAM are just a couple of the solutions

  35. Fast NICs • The server part of the network needs to run faster than other parts of the network • For example, if your PCs run at 10 Mbps, then use a switch with a 100 Mbps port attached to a server using a 100 Mbps NIC

  36. Smarter NICs • Use NICs with onboard processors that do most of the processing work instead of using the CPU

  37. Full-Duplex NICs • Full-duplex NICs can send and receive at the same time…doubling the speed of the network • Make sure the switch or hub can use full-duplex

  38. Make the Drives Faster • SCSI is faster than PATA • RAID 5 provides data transfer speeds that match those of a single drive, plus provides data redundancy

  39. It’s Not Just Hardware • Faster CPUs, more RAM, powerful NICs, and fast hard drives is just part of the answer to making servers perform well • Good maintenance, defragging, disk caches all add to performance

  40. Reliability

  41. Good Power • Dedicated circuits restrict the outlets and usually have bright orange faceplates • Putting too many items on a circuit may cause the power to sag or the circuit breaker to flip off • Surge suppressors provide protection against unexpected surges or spikes in voltage • Uninterruptible Power Supplies (UPS) will provide protection from surges, sags, and power outages • Backup power may come in the form a second power supply or a diesel backup system

  42. Computer Virus • Symptoms of a computer virus include • Unusual sluggishness • Strange error messages • Lock ups • No symptom at all! • Viruses have two functions • Proliferate (make copies of itself) • Activate (at some signal, count, date)

  43. Types of Viruses • Boot sector • Changes the code in the Master Boot Record (MBR) of the hard drive • Executable • Reside inside executable files and run when the file is executed • Macro • Specially written macros that auto-start when an application is run • Trojan • Freestanding program that does something other than what the person thinks they do

  44. Types of Viruses • Bimodel/Bipartite • Uses both boot-sector and executable functions • Worm • Spreads through applications like e-mail and web browsers

  45. Antivirus Programs • Antivirus programs protect your computer against viruses • May actively be used to scan the master boot record and files on the PC • May act as a virus shield that passively monitors your PC • Use a library of signatures to help identify viruses

  46. Virus Traits • Polymorphics/Polymorphs • A virus that attempts to change its signature to prevent detection • Virus programs may create a checksum on files that is used for comparison each time the program is run • Stealth • Most are boot sector viruses that try to hide from antivirus software

  47. Virus Prevention Tips • Avoid getting one – know where your software and files are coming from • Use an antivirus shield • Keep a bootable, write-protected floppy with a copy of an antivirus program

  48. Environment • Keep the server room locked at all times • Keep the humidity around 40% • Keep the room a bit cool around 68°

  49. Redundant Components • Use servers with redundant power supplies • Use redundant NICs that can take over if one dies or be replaced without rebooting • Use duplexing rather than mirroring • Mirror your entire server if you have the money

  50. Which Server is Right? • What is the server going to be doing? • How many users will connect to the server? • How much fault tolerance do you need? • The “server that never goes down” is very expensive and may not be justified • How much processing power do you need (CPUs) and how much RAM? • How scalable is your server? Can it be upgraded easily? Can additional servers be added?

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