Data Storage Network Technologies -WILP MTech. sem 3 BITS pilani

1. BITS Pilani
Pilani Campus
Data Storage Technologies
& Networks
Dr. Virendra Singh Shekhawat
Department of Computer Science and Information Systems

2. BITS Pilani, Pilani Campus
Topics
• Network Attached Storage (NAS)
– Storage Array Types
– What is NAS….?
– File Systems Functions
– File System for Network Storage vs. Traditional File
System
– NAS Systems/Architectures
• Gateway NAS and NAS Appliances
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3. BITS Pilani, Pilani Campus
Storage Arrays Types
• SAN
– Provides connectivity via FC, FCoE, iSCSI, SCSI (SAS)
– Uses low level disk drive access commands like READ block,
WRITE block, and READ capacity
• NAS
– Provides connectivity over file based protocols like Network
File System (NFS), SMB/CIFS (Server Message Block/Common
Internet File System)
– Uses high level file based protocols
– Commands: create a file, rename a file, lock a byte range
within a file etc.
• Unified (SAN and NAS)
– Shared storage over both file and block protocols (aka
multiprotocol arrays)
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4. BITS Pilani, Pilani Campus
Storage on the Network
• What does a Computer Network achieve?
– Communication
• Complexity management for computation
– Local computation vs. Non-local Computation
• Collaboration
• Persistent Shared Data
– Data is accessible to (or accessible through) multiple
computers and persistent across computations
– Storage is shared by multiple computers i.e. available
on a network
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5. BITS Pilani, Pilani Campus
Network Attached Storage (NAS)
• NAS drives examples:
– Windows
• Shares or network shares
• Supports mapping of external file systems on local machine as drive
name
– Linux
• Exports or NFS exports
• NFS exports are usually mounted to a mount point within the root
file system 5
NAS
Head
R/W file
Block I/O to
Disk drives
NAS Backend
(Disk drives)
Client

6. BITS Pilani, Pilani Campus
Network Attached Storage
• Storage units are on the network
– Network is the same as the compute network (LAN)
– Data is accessed as files from file systems
• File Systems are supported by file servers (NAS servers)
• Novell’s file servers were one of the earliest networked file
servers.
• NAS systems come in different configurations:
– Server including FM and FS and direct attached
storage
– NAS head (only the FM) separate from the FS
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7. BITS Pilani, Pilani Campus
NAS Architectures
• NAS Server
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• NAS Gateway

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File Systems
• File systems form an intermediate layer between
block oriented hard disks and applications with a
volume manager
– Manage the blocks of the disk
– Make available to users and applications via
directories and files
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9. BITS Pilani, Pilani Campus
File Systems Functions
• Journaling
– Ensure consistency of the file system even after a system
crash
– Every change in the file system is first recorded in a log
file
• Snapshots
– To freeze the state of the file system at a given point of
time (state of the data should be consistent)
– It loads server’s CPU and hardware independent
• Dynamic File System Expansion
– Volume manager
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10. BITS Pilani, Pilani Campus
NAS Systems
• File Servers
– Operating System Implementation
• Customized Operating Systems
– Typically thinned versions of Linux or Windows
• Most tasks are I/O bound (particularly file I/O)
– Simpler scheduling and task management
– No user management or user interaction required
• Restricted Memory allocation model (Mostly for buffering)
– No heap needed
– Limited stack size
• Tasks are (soft) real-time
– At the server level, I/O requests must have time-bounds to provide
performance guarantees
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11. BITS Pilani, Pilani Campus
NAS Arrays: Scaling
• Multiple individual NAS arrays can be deployed
– e.g. per project one NAS array
– Drawback
• Management becomes tedious
• Single Global Namespace or single file system
(scale-out NAS system)
– Adding more servers with CPU + memory + storage
– One file system on the network accessed by all nodes
– Called as NAS clusters
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12. BITS Pilani, Pilani Campus
Example
• Multiple Individual NAS Arrays
• NAS Cluster
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13. BITS Pilani, Pilani Campus
Thank You!
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