Transcript Servers - Wright State University

CEG 2400 Fall 2012
Network Servers
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Network Servers
• Critical Network servers
– Contain redundant components
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Power supplies
Fans
Memory
CPU
Hard Drives
– Provide fault tolerance, load balancing
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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.
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Network File System Components
• Disk Partitions
– Dividing the physical disk into one or more
partitions (parts) in order to format and manage
data storage
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Disk Drive Categories
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Integrated Drive Electronics (IDE)
Enhanced Integrated Drive Electronics (EIDE)
Advance Technology Attachments (ATA)
Serial ATA (SATA)
Small Computer System Interface (SCSI)
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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
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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
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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
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File Shares
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A Major Network Service
– Sometimes called a directory share
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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
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File Shares
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Network Server
Fault Tolerance
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Server Mirroring
Server Clustering
RAID storage
NAS (Network Attached Storage)
SAN (Storage Area Networks)
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
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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
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Server Mirroring
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
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Server Clustering
• Many advantages over mirroring
– Each clustered server
• Performs data processing
• Always ready to take over
– Reduces ownership costs
– Improves performance
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Server Clustering
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
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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
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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
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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
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RAID
RAID level 0 - disk striping
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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
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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
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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
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Writes data more rapidly
Uses several disks for parity information
Disk replacement causes little interruption
Controlling software regenerates failed file parts
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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
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RAID
RAID level 5 - disk striping with distributed parity
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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
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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
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NAS
Network attached storage on a LAN
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Storage
• SANs (Storage Area Networks)
• Distinct network of storage devices
• Communicate directly
– With each other, other networks
• Multiple storage devices
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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
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SANs
• Drawbacks
– High cost
– More complex than NAS, RAID
• Training, administration efforts required
• Use
– Environments with huge data quantities requiring
quick availability
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SAN area network
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Network Servers Summary
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Network File System
Mirroring vs Clustering
RAID levels – 0, 1, 5
Network attached storage (NAS)
Storage area networks (SAN)
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End of Network Servers
Questions
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