1. The Building Blocks of NAS
Introduction
This lesson introduces the building blocks of Network Attached Storage (NAS). The lessons explain the basic characteristics of a NAS device, advantages and disadvantages of NAS, file server consolidation using NAS, and the architecture of a NAS client and a NAS server. The lesson also covers departmental NAS solutions, NAS scaling, and NDMP and NAS backups.
Importance
Understanding the basics of NAS is important to the Cisco Systems Engineer (SE) working in the storage field in order to understand the relationship between NAS and other storage technologies such as SAN and Direct Attached Storage (DAS).
© 2003, Cisco Systems, Inc. All rights reserved. 1

2. Lesson Objective
Upon completion of this lesson, you will be able to explain basic NAS building blocks.
Performance Objective
Upon completion of this lesson, you will explain basic NAS building blocks.
Enabling Objectives
Explain the basic characteristics of a NAS device
Explain the advantages and disadvantages of a NAS device
Explain file server consolidation using NAS devices.
Explain the architecture of a NAS client and a NAS server
Explain the basic characteristics and functions of a NAS Head
Explain departmental NAS solutions.
Explain the problem of, and solution to, NAS scaling.
Explain the significant problems associated with NAS backups
Explain the various functions of Network Data Management Protocol (NDMP) for solving problems associated with NAS backup

3. Lesson Outline What is NAS? NAS advantages and disadvantages
Consolidating storage with NAS
Architecture of a NAS client and server
The NAS Head
Departmental NAS solutions
NAS scaling
Problems with NAS backups
Network Data Management Protocol (NDMP)
NAS backup before and after NDMP
Summary
Prerequisites
Curriculum Unit 1, all Module 1 lessons and Module 2 lesson "File Sharing for NAS and SAN"

4. Network Attached Storage
What is NAS?
Network Attached Storage
NAS File Server
File serving “appliance”
Attached to existing LAN
Optimized operating system
Heterogeneous client access
What is NAS?
Objective
Explain the basic characteristics of a NAS device.
Introduction
This section introduces the basic characteristics of NAS.
Definition
NAS stands for "Network Attached Storage.“ NAS file serving appliances are "plug and play" storage systems that allow end users to share files with each other.
Facts
The NAS Server typically has:
One or more Ethernet LAN interfaces–usually 10/100/1000.
A processor that runs a ‘thin’ operating system—sometimes the thin OS is called a micro-kernel.
Automated software for effortless installation by administrators and easy access by end users.
NAS systems relieve administrators from the drudgery of loading operating systems and software and then connecting it to the network and integrating it into the network environment. NAS products come ready to run on Unix and Windows environments.
Example
A number of vendors make NAS devices. Network Appliance is one of the current industry leaders.

5. NAS Advantages and Disadvantages
Multi-protocol
Storage consolidation
More flexible than DAS
Universal client access
Easy to install and configure
Disadvantages
Limited scalability
Increased LAN traffic
Additional I/O processing
NAS Advantages and Disadvantages
Objective
Explain the advantages and disadvantages of a NAS device.
Introduction
This section introduces the advantages and disadvantages of NAS.
Facts
NAS has many advantages, including:
Multiple separate file servers (such as CIFS and NFS servers - see Module 1, lesson 4 on File Systems) ) can be combined into a single multi-protocol file server.
Overcomes several of the limitations of Direct Attached Storage (DAS) including ease of expansion.
Allows clients from heterogeneous operating systems to share the same files.
NAS filers are extremely simple to install and configure.
NAS disadvantages include:
Often claimed that in NAS there is a limited ability to easily and transparently increase the amount of storage resources
Compared to DAS, NAS increases the I/O load on the network
Compared to DAS, additional CPU processing is required to utilize network layer protocols
Practice - NAS Advantages and Disadvantages
List potential advantages and disadvantages of NAS.

6. Consolidating Storage with NAS
Windows Clients
Unix Clients
CIFS
NFS
NAS Storage
Consolidating Storage with NAS
Objective
Explain file server consolidation using NAS devices.
Introduction
This section explains how file server consolidation can be done using a NAS storage solution.
Facts
In addition to the advantages of consolidating direct attached storage, file server consolidation has been a driver for NAS. File serving that was formerly done using separate servers for each type of platform (Windows and Unix) can now be consolidated.
Without consolidation, separate administrators are often required for each environment, which adds costs for IT organizations.
With separate file servers, data duplication and version control across platforms may become challenging. A NAS appliance eliminates the need for separate file servers.
Windows
File Servers
UNIX
File Servers
Heterogeneous

7. Architecture of a NAS Client and Server
Host Bus
Adapter (HBA)
Device Driver
File System
Disk Drive
Tape Drive
Application
I/O Interface (SCSI)
Operating System (O/S)
Network
Interface Card
NIC Driver
Network File
System
NAS Filer
Client
System Bus
LAN
= NAS I/O Path
Network File Redirection
= NAS I/O Path
Architecture of a NAS client and NAS server
Objective
Explain the architecture of a NAS client and NAS server.
Introduction
This section introduces the basic architecture of a NAS Client.
Facts
Architecture of a NAS client
The fundamental enabler for NAS is the ability for File I/O to be redirected over a network. File I/O involves issuing commands to open and close files as well as reading bytes of data from the file and writing bytes of data to the file.
A driver in the client system interprets each file I/O request to determine if it should be conveyed over the LAN. If so, it uses the underlying protocol stack and system functions to transmit the file request over the LAN to a NAS system, which then performs the actions requested.
Continued…
Architecture of a NAS Client

8. Architecture of a NAS Client and Server (cont.)
Filing Protocols
NFS CIFS SMB HTTP
Data and Storage Management Tools
NAS Operating System Kernel
TCP/IP
File System
Phy, MAC Ethernet FDDI ATM
Storage Interface
SCSI, FC, IDE
Volume Manager
Network
Storage Bus or Network
Architecture of a NAS client and NAS server (cont.)
Facts
Architecture of a NAS server
As opposed to general purpose application servers, NAS systems are highly optimized for network protocol file system processing.
The NAS operating system scheduler determines which processes get processor time and memory, and the NAS file system manages the address space for its storage. Among other things, the operating system must provide sophisticated locking enforcement policies to insure multiple clients do not write to the same files simultaneously.
Management functions that allow for simple provisioning and access controls are critical to the success of NAS.
A good example of a NAS filer operating system is NetApp Data ONTAP. This system provides support for multiple network protocols, as well as the NetApp Write Anywhere File Layout (WAFL) file system. It supports RAID volume management of SCSI or FC attached storage and provides advanced features such as multi-level snapshot capability for storing and retrieving multiple versions of files.
Some NAS systems are built using stripped down general purpose operating systems such as UNIX, Linux, BSD or Microsoft Windows with the MS Server Appliance Kit (SAK). In general these are not as highly optimized and do not perform as well as dedicated purpose NAS operating systems from NetApp, EMC, and others.
Architecture of a NAS Server

9. The NAS Head Attaches to LAN and SAN File I/O on LAN Block I/O on SAN
Clients
Attaches to LAN and SAN
File I/O on LAN
Block I/O on SAN
Scalability
Storage Consolidation
LAN Free Backup
NAS-SAN Convergence
LAN
NAS Head
The NAS Head
Objective
Explain the basic characteristics and functions of a NAS Head
Introduction
This section introduces the characteristics and functions of a NAS Head in Enterprise Storage.
Facts
An emerging development in NAS is the NAS ‘Head’. NAS heads are also known as NAS gateways. The NAS Head is a device that connects to an Ethernet LAN on one side and typically a Fibre Channel SAN on the other. The NAS Head performs file level I/O on the LAN side and block level I/O on the SAN side.
Benefits of the NAS Head include:
Easier to add storage capacity when needed
Consolidation of storage resources into a single secure location
Enabling LAN free backups of the storage arrays
In the diagram shown, the server has access to both a NAS Head and a NAS filer as well as direct access to the SAN. As NAS and SAN environments converge, expect to see a growth in the popularity of NAS Heads over NAS filers.
Example
EMC has offered a NAS Head solution for years with their Celerra product line. Network Appliance recently announced an agreement to supply NAS Heads to Hitachi to front Hitachi’s disk subsystems with Network Appliance’s filing technology.
Continued…
App Server
NAS Filer
SAN
Tape Library
Storage Array

10. Departmental NAS Solutions
Objective
Explain departmental NAS solutions.
Introduction
This section introduces NAS departmental solutions.
Facts
Departmental NAS solutions often employ low-priced entry level NAS “appliance” type devices intended for the small office, department or business use. They are relatively inexpensive compared to enterprise level products. For example, some are priced at under $1000. On the other hand, high-end NAS filers can cost over $100,000 depending on the amount of storage capacity, support for redundancy, etc.
Practice - Departmental NAS Solutions
What are departmental NAS solutions?

11. NAS Scaling G:\ G:\ G:\ G:\ M:\ M:\ M:\ M:\ NAS Scaling Issue Folder
Out of Capacity
1, 2, 3, N applications and end users
M:\
Folder
M:\
Folder
M:\
Folder
M:\
Folder
NAS Scaling
Objective
Explain the problem of, and solution to, NAS scaling.
Introduction
This section introduces the problem of, and solution to, NAS scaling.
Facts
If NAS is so easy, why doesn’t everybody just buy NAS and make things easier?
The answer is due to the fact that NAS has problems related to scalability. When a business runs out of capacity on a NAS system, the obvious first reaction is just to roll in another one and plug it in and start using it.
However, if one needs to expand the space for the applications on a NAS system one already has, the data from the first NAS system might need to be moved to the new one.
If that is the case, it is necessary to change or create new mount points for all applications and users accessing the NAS server. If this means hundreds of client-side updates, it can be a huge amount of administrative work!
Continued…
N + 1 NAS Appliance
NAS Scaling Issue

12. 1. 2. NAS Scaling (cont.) G:\ G:\ G:\ NAS Scaling Solutions
Forklift Upgrade
Coalesced IP 1. 2.
Data Migration
G:\
Folder
G:\
Folder
G:\
Folder
NAS Scaling (cont.)
Facts
There are two traditional ways to solve the scaling issue:
Forklift upgrade of the NAS system to a larger one
Create a NAS cluster and somehow coalesce the IP addresses so cluster resources look like they belong to a single NAS image on the network
In addition, as noted earlier, NAS scaling could be addressed through the use of a NAS Head.
Examples of NAS clustering solutions include:
NetApp Cluster
Dell PowerVault 75xN NAS Cluster
HPQ StorageWorks NAS Cluster
No Change
NAS Cluster
NAS Scaling Solutions

13. Problems with NAS Backup
Initially, as NAS systems grew in size, backup became a significant problem
Network backup is sometimes used, but ...
Limited backup agent support for NAS platforms
Tape device support was difficult for NAS vendors
Problems with NAS Backup
Objective
Explain the significant problems associated with NAS backups.
Introduction
This section introduces the learner to significant problems associated with NAS backups.
Facts
As NAS systems grow in size, backup becomes a significant problem. Network backup is sometimes used; however, there are several problems:
Backups do not always finish within the backup window. Backups consume network bandwidth.
Backup agent support may not be available for NAS platforms. Additionally, scaled down NAS operating systems did not support APIs and services for backup software agents.
Tape device support was limited for NAS vendors.
A more significant issue is that there are hundreds and hundreds of combinations of backup devices and drivers. NAS vendors do not have the resources to test them with their stripped down operating systems.
Because the operating systems are stripped down, backup vendors such as Veritas, Legato and CA will not write backup agents for those NAS platforms.

14. Network Data Management Protocol
Open standard for NAS backup
Enables creation of “universal agent” for NAS
Supports LAN-free and serverless backup
Backup host is considered NDMP client
NAS operating system must support NDMP
(ref:
Network Data Management Protocol
Objective
Explain the various functions of NDMP for solving problems associated with NAS backup.
Introduction
This section defines NDMP and indicates its importance in solving backup problems in NAS environments.
Facts
NDMP solves the problems associated with backing up NAS by providing a remote control system for NAS backup.
NDMP is an open standard protocol for enterprise-wide backup of heterogeneous network-attached storage. NDMP was co-invented by Network Appliance and PDC Software (now part of Legato Systems, Inc.). In April 2000, a new work group for NDMP was formed as part of SNIA and is responsible for the development of the protocol standard, interoperability testing, and educational programs for NDMP. 
Both the Backup system (NDMP client) and the NAS system (NDMP server) need to have a special NDMP code to work.
NDMP backup data can also be re-routed over the network to another NDMP system with a tape drive if the NAS system does not have a working tape drive attached.

15. Network Data Management Protocol (cont.)
NAS Filer
Backup Host
Control Path
Backup DB
LAN
Data Path
Parallel SCSI
1. Backup host controls backup and writing of data to tape device
2. Data path passes through LAN and backup host to tape device
3. Backup database stored on backup host
Network Data Management Protocol (cont.)
Facts
In a traditional network backup, the backup host runs backup software that initiates a backup according to a pre-determined backup schedule. Data is transferred across the LAN and passes through the backup host. The backup host writes data to a tape device that is often directly attached. The backup host keeps a local record of backup transactions to assist in data recovery.
Tape Device
NAS Backup before NDMP

16. Network Data Management Protocol (cont.)
Data Management Application “NDMP Client”
NDMP Host “NDMP Server”
Tape Device
Parallel SCSI or SAN
Control Path
LAN
Backup DB
1. NDMP client sends commands to NDMP server
2. Data is written directly to tape device, bypassing LAN
3. Backup database stored on backup host
Network Data Management Protocol (cont.)
Facts
The NDMP architecture is based on a client server model. NDMP compliant backup software, which is referred to as the Data Management Application (DMA), is considered to be the client. A DMA interacts with one or more NDMP servers, managing the transfer of data between server resident NDMP data and tape services.
NDMP clients are able to communicate with NDMP aware filers to perform LAN-free backups as illustrated above. The NDMP client initiates the backup by sending commands that essentially say “read a selected range of blocks and write them directly to the designated tape device”. The tape device can be directly connected or connected to another NDMP server.
The NDMP client uses control connections to manage the NDMP server. These control connections are implemented as TCP/IP sockets. Messages flow in both directions on a control connection. The client sends messages to the server for the purpose of managing the operations of the NDMP service. The server sends notifications when it requires attention, or file history information about the content of the data stream. The NDMP servers must be connected to the LAN for TCP/IP based NDMP control connections.
A SCSI pass through service allows an NDMP client to issue SCSI commands to a device such as a tape robot. This service allows the client to control other devices such as a tape or CD media changer.
Virtually all NAS vendors now include NDMP support in their operating systems, including NetApp, EMC, Auspex, and many others.
Similarly, most backup vendors now offer NDMP support in their products. Some examples include HP's Data Protector, Veritas NetBackup, Tivoli Data Protection for NDMP and Legato NetWorker
NAS Backup after NDMP

17. Consolidating Storage with NAS Practice
A client informs you that they are going to upgrade their storage environments, but would like to trim IT maintenance costs. They currently run Windows and Unix file servers with administrators for each environment. How can NAS help them to cut costs?
Practice - Consolidating Storage with NAS

18. NAS Scaling Practice
Forklift Upgrade
Coalesced IP 1. 2.
Data Migration
Based on the diagram, explain two traditional ways to solve the scaling issue.
Practice - NAS Scaling

19. Network Data Management Protocol Practice
NDMP Host “NDMP Server”
Data Management Application “NDMP Client”
Control Path
Backup DB
LAN
Parallel SCSI or SAN
Practice - Network Data Management Protocol
Explain how the diagram illustrates the role of NDMP in NAS backup.
Tape Device

20. The NAS Head Practice
Clients
LAN
Explain the function of a NAS head in the diagram.
NAS Head
Practice - The NAS Head
Explain the diagram, noting the connections, and the function of the NAS Head.
App Server
NAS Filer
SAN
Tape Library
Storage Array

21. What is NAS? Practice
From the list below, pick the items that apply to a typical NAS appliance
A full-featured operating system
Empty slots for 10/100/1000 ethernet LAN interfaces
A "thin" operating system
10/100/1000 LAN interfaces preinstalled
"Plug and play"
Automated installation software
Complex installation
NAS File Server
Practice - The Function of NAS
Answer the following questions
What is NAS?
Give an overview of the basic characteristics of NAS

22. Architecture of a NAS Client Practice
Answer the following questions:
What ability is the fundamental enabler for NAS?
What is the function of the driver in the client system?
Practice - Architecture of a NAS client

23. Architecture of a NAS Server Practice
Data and Storage Management Tools
TCP/IP
Phy, MAC Ethernet FDDI ATM
Storage Interface
SCSI, FC, IDE
Volume Manager
Network
Storage Bus or Network
Practice - Architecture of a NAS server
Instructions
Identify and explain the function of the missing components in the above diagram.
Architecture of a NAS Server

24. Lesson Practice
In groups of two or three, answer the following questions. Be prepared to share your answers with the class.
1. List the building blocks of NAS.
2. Explain three advantages and three disadvantages of NAS
3. What is the function of a NAS head, and how does this impact NAS scaling?
4. What is the importance of NDMP in a NAS environment?
Practice - The Building Blocks of NAS Lesson Practice

25. Summary This lesson presented these key points:
NAS (Network Attached Storage) makes use of file level I/O. NAS, like DAS and SAN has both disadvantages.
NAS can be used to consolidate storage.
Problems with NAS scaling can be addressed several different ways, including the use of a NAS head.
NDMP is an important solution to the problems associated with NAS backup.
Summary: The Building Blocks of NAS
Review
In this lesson, you learned how to explain NAS building blocks. This lesson introduced the building blocks of Network Attached Storage (NAS). The lessons explained the basic characteristics of a NAS device, advantages and disadvantages of NAS, file server consolidation using NAS, and the architecture of a NAS client and a NAS server. The lesson also covered departmental NAS solutions, NAS scaling, and NDMP and NAS backups.