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CEG 2400 Fall 2012 Network Servers

Learn about critical network servers, redundant components, fault tolerance, load balancing, network file systems, disk drive categories, fault tolerance in network file systems, drive volumes, universal naming convention, drive mappings, file shares, server fault tolerance options like mirroring and clustering, and RAID storage.

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CEG 2400 Fall 2012 Network Servers

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  1. CEG 2400 Fall 2012Network Servers 1

  2. Network Servers • Critical Network servers • Contain redundant components • Power supplies • Fans • Memory • CPU • Hard Drives • Provide fault tolerance, load balancing

  3. Network File System • A network file system is a design for storing files on one or more hard disks on the servers on the network • File system refers to the file storage structure on an individual server, whereas network file system refers to how file storage is structured across all servers in the network • Microsoft uses NTFS, FAT32, or FAT and Linux/Unix uses NFS, UFS, Reiser, ext4, and many others.

  4. Network File System Components • Disk Partitions • Dividing the physical disk into one or more partitions (parts) in order to format and manage data storage

  5. Disk Drive Categories • Integrated Drive Electronics (IDE) • Enhanced Integrated Drive Electronics (EIDE) • Advance Technology Attachments (ATA) • Serial ATA (SATA) • Small Computer System Interface (SCSI)

  6. Network File System Components • Fault tolerance is essential because having all operating system files and data on one drive creates a potential single point of file service failure if the drive crashes • Hot Fix detects bad disk blocks and automatically redirects the data being written to a reserved area

  7. Network File System Components • Volumes or drives are the basic storage unit in the network file system that gives users access to the network directories and files • Microsoft supports both static and dynamic drives • Dynamic drives can be made bigger

  8. Universal Naming Convention and Drive Mappings • Two Ways to access resources • Most modern NOSs recognize Universal Naming Convention (UNC) paths, a standard method for specifying network resources • \\servername\sharename • In UNC-aware applications and many command-line activities, a UNC path can be used instead of a drive letter to access a network resource • Drive mapping: process of associating a network storage resource with a local drive letter

  9. File Shares • A Major Network Service • Sometimes called a directory share • Accessed one of three ways • By mapping a drive • By using a UNC (universal naming convention) name • By selecting the share from a list

  10. File Shares

  11. Network ServerFault Tolerance • Server Mirroring • Server Clustering • RAID storage • NAS (Network Attached Storage) • SAN (Storage Area Networks)

  12. Server Mirroring • Mirroring • Fault-tolerance technique • One device duplicates another's activities • Server mirroring • One server continually duplicates another's transactions, data storage • Uses identical servers, components • High-speed link between servers • Synchronization software • Form of replication • Dynamic copying of data from one location to another

  13. Server Mirroring • Advantage • Flexibility in server location • Disadvantages • Time delay for mirrored server to assume functionality • Toll on network as data copied between sites • Hardware and software costs • May be justifiable

  14. Server Mirroring

  15. Server Clustering • Links multiple servers together • Act as single server • Clustered servers share processing duties • Appear as single server to users • Failure of one server • Others take over • For large networks • More cost-effective than mirroring

  16. Server Clustering • Many advantages over mirroring • Each clustered server • Performs data processing • Always ready to take over • Reduces ownership costs • Improves performance

  17. Server Clustering

  18. Storage • Data storage: also has issues of availability and fault tolerance • What happens when hard drive stops working • Different methods are available for making sure shared data and applications are never lost or irretrievable

  19. RAID (Redundant Array of Independent [or Inexpensive] Disks) • Collection of disks • Provide shared data, application fault tolerance • Disk array (drive) • Group of hard disks • RAID drive (RAID array) • Collection of disks working in a RAID configuration • Single logical drive • There are many different levels of RAID configurations

  20. RAID • Hardware RAID • Set of disks, separate disk controller • RAID array managed exclusively by RAID disk controller • Attached to server through server’s controller interface • Software RAID • Software implemented, controls RAID techniques • Any hard disk type • Less expensive (no controller, disk array) • Performance rivals hardware RAID

  21. RAID Levels • RAID Level 0 - Disk Striping • Simple RAID implementation • Data written in 64-KB blocks equally across all disks • Not fault-tolerant • Does not provide true redundancy

  22. RAID level 0 - disk striping RAID

  23. RAID • RAID Level 1- Disk Mirroring • Disk mirroring provides redundancy • Data from one disk copied automatically to another disk • Dynamic data backup • Data continually saved to multiple locations • Advantages • Simplicity, automatic and complete data redundancy

  24. RAID • Disk Duplexing • Related to disk mirroring • Data continually copied from one disk to another • Separate disk controller used for each disk • Provides added fault tolerance • Disadvantages • Cost of two controllers, software for mirroring

  25. Raid Level 1

  26. RAID • RAID Level 5 - Disk Striping with Distributed Parity • Most popular data storage technique • Data written in small blocks across several disks • Parity error checking information distributed among disks • Advantages • Writes data more rapidly • Uses several disks for parity information • Disk replacement causes little interruption • Controlling software regenerates failed file parts

  27. RAID • RAID Level 5 - Disk Striping with Distributed Parity (con’t) • Hot spare (hot swappable component) • Array disk, partition used only when one RAID disk fails • Cold spare • Duplicate component • Not installed

  28. RAID level 5 - disk striping with distributed parity RAID

  29. StorageNAS vs. SAN • NAS (Network Attached Storage) • Specialized storage device, storage device group • Provides centralized fault-tolerant data storage • Difference from RAID • Maintains own interface to LAN

  30. NAS • Advantages • NAS device contains own file system • Optimized for saving, serving files • Reads, writes fast • Easily expandable • No service interruption • Disadvantage • No direct communication with network clients • Use • Enterprises requiring fault tolerance, fast data access

  31. Network attached storage on a LAN NAS

  32. Storage • SANs (Storage Area Networks) • Distinct network of storage devices • Communicate directly • With each other, other networks • Multiple storage devices

  33. SANs • Advantages • Fault tolerant • Fast • Special transmission method • Fiber-optic media, proprietary protocols • Example: Fibre Channel, IP storage (iSCSI) • Install in location separate from LAN served • Provides added fault tolerance • Highly scalable • Faster, more efficient method of writing data

  34. SANs • Drawbacks • High cost • More complex than NAS, RAID • Training, administration efforts required • Use • Environments with huge data quantities requiring quick availability

  35. SAN area network

  36. Network Servers Summary • Network File System • Mirroring vs Clustering • RAID levels – 0, 1, 5 • Network attached storage (NAS) • Storage area networks (SAN)

  37. End of Network Servers Questions 37

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