1 CEG 2400 Fall 2012 Network Servers

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

3 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. Network File System

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

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 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 Network File System Components

7 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 Network File System Components

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 1.By mapping a drive 2.By using a UNC (universal naming convention) name 3.By selecting the share from a list

10 File Shares

Network Server Fault 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

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

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 RAID level 0 - disk striping

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

Raid Level 1

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 26

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 RAID level 5 - disk striping with distributed parity

29 Storage NAS 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 NAS Network attached storage on a LAN

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

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 33

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