04/22/2304/22/23 11

BASIC CONCEPTS OF STORAGE BASIC CONCEPTS OF STORAGE

DAS – NAS –SANDAS – NAS –SAN

TECHNOLOGY INFRASTRUCTURE TECHNOLOGY INFRASTRUCTURE SERVICESSERVICES

AuthorAuthor JoshuaJoshua

TeamTeam TISTISDate of CreationDate of Creation May 20, 2005May 20, 2005Wipro email idWipro email id Joshua.micheal@wipro.comJoshua.micheal@wipro.com

04/22/2304/22/23 22

OverviewOverview : :

DAS – NAS - SANDAS – NAS - SAN

BASIC CONCEPTSBASIC CONCEPTS

SOFTWARE ARCHITECTURESOFTWARE ARCHITECTURE

MERITS AND DEMERITSMERITS AND DEMERITS

04/22/2304/22/23 33

Storage Area NetworkStorage Area Network Architectures & Technology Architectures & Technology

Businesses and other organizations require Businesses and other organizations require effective way to store and maintain data.effective way to store and maintain data.

The following discussion examines three The following discussion examines three categories of data storage technologies includingcategories of data storage technologies including

1.Direct Attached Storage - 1.Direct Attached Storage - DAS

2.Network Attached Storage - 2.Network Attached Storage - NAS 3.Storage Area Networks - 3.Storage Area Networks - SANs

04/22/2304/22/23 44

Direct Attached StorageDirect Attached Storage Storage is directly attached to a standalone PCs, Storage is directly attached to a standalone PCs,

Workstations and Servers.Workstations and Servers.

DAS configuration can be one or several hard disk DAS configuration can be one or several hard disk drives or disk arraysdrives or disk arrays

Data is transferred using SCSI commandsData is transferred using SCSI commands

Standard buses are used between the HDDs and Standard buses are used between the HDDs and the computers, such as SCSI, ATA , SATA and FCthe computers, such as SCSI, ATA , SATA and FC

04/22/2304/22/23 55

Direct Attached Direct Attached StorageStorage

04/22/2304/22/23 66

DAS Software ArchitectureDAS Software Architecture

04/22/2304/22/23 77

• The DAS disk system is managed by the client OS.The DAS disk system is managed by the client OS.

• Software applications access data via file I/O system calls into Software applications access data via file I/O system calls into the OS.the OS.

• The file I/O system calls are handled by file system, which The file I/O system calls are handled by file system, which manages the directory data structure and mapping from files to manages the directory data structure and mapping from files to disk blocks in an abstract logical disk space.disk blocks in an abstract logical disk space.

• The volume manager manages the blocks resources that are The volume manager manages the blocks resources that are located in one or more physical disks in the disk system and located in one or more physical disks in the disk system and maps the accesses to the logical disk block space to the physical maps the accesses to the logical disk block space to the physical volume/cylinder/sector address.volume/cylinder/sector address.

• The disk system device driver ties the OS to the disk controller The disk system device driver ties the OS to the disk controller or HBA hardware that is responsible for the transfer of commands or HBA hardware that is responsible for the transfer of commands and data between the client computer and the disk system.and data between the client computer and the disk system.

• The file level I/O initiated by the client application is mapped intoThe file level I/O initiated by the client application is mapped into block level I/O transfers that occurs over the interface between block level I/O transfers that occurs over the interface between

the the client computer and the disk systemclient computer and the disk system

04/22/2304/22/23 88

Merits of DAS Approach :Merits of DAS Approach : Ease to implement and manage on a small Ease to implement and manage on a small

scale.scale. cost effective on a small Scale.cost effective on a small Scale.

Demerits of DAS Approach :Demerits of DAS Approach :

High Cost of Management.High Cost of Management. Distance Limitations.Distance Limitations. Limited Availability.Limited Availability.

04/22/2304/22/23 99

High Cost of Management.High Cost of Management.

1.1. The storage capacity of the DAS is limited by The storage capacity of the DAS is limited by the number of HDDs supported by the bus. In the number of HDDs supported by the bus. In order to increase storage capacity order to increase storage capacity enterprises must purchase more servers.enterprises must purchase more servers.

2.2. To protect the data on the DAS systems, To protect the data on the DAS systems, backup/recovery of data is required for each backup/recovery of data is required for each computer,computer,

since it is a time consuming process that since it is a time consuming process that effects the performance of the computers.effects the performance of the computers.

3. Repairing the failures on the individual 3. Repairing the failures on the individual computers requires even more manual work. computers requires even more manual work. All these factors increase the total cost of All these factors increase the total cost of ownership of DAS systems.ownership of DAS systems.

04/22/2304/22/23 1010

Distance Limitations : Storage device must be Distance Limitations : Storage device must be located close to the server since SCSI devices located close to the server since SCSI devices are designed to work over parallel cable with are designed to work over parallel cable with max length of 12 meters.max length of 12 meters.

Limited Availability :Limited Availability :

1.1. Adding/Removing a disk drive may disrupt Adding/Removing a disk drive may disrupt access to all the disk s on the SCSI Chain.access to all the disk s on the SCSI Chain.

2.2. Any server failure results in the content on the Any server failure results in the content on the attached storage resources becoming in attached storage resources becoming in accessible. If the storage server is decoupled accessible. If the storage server is decoupled from the server, then backup server can be from the server, then backup server can be used to take control of the storage and provide used to take control of the storage and provide access to data.access to data.

3. The efficiency of the storage resource is low , 3. The efficiency of the storage resource is low , as storage capacity is bound to a given server. as storage capacity is bound to a given server. Sharing storage resources over the network is Sharing storage resources over the network is not recommended in DAS model.not recommended in DAS model.

04/22/2304/22/23 1111

Network Storage Network Storage AttachedAttached

04/22/2304/22/23 1212

NAS is a file based storage architecture with

resources attached directly to the LAN.

NAS is a storage appliance that consists of a high performance file server that plugs into a LAN and optimized for file serving, i.e., storing, retrieving and serving files.

NAS device use file- sharing protocols such as NFS - Network File System , Common Internet File System - CIFS and Internet Protocol Exchange – IPX to manage data request.

NAS use various network protocols such as HTTP, FTP and TCP/IP.

NAS I/O requests are called “file I/Os”“file I/Os”

04/22/2304/22/23 1313

NAS Software ArchitectureNAS Software Architecture

The NAS storage system involves two types of devices: the client computer system andThe NAS storage system involves two types of devices: the client computer system and NAS devices. The NAS devices present storage resources onto the LAN network that NAS devices. The NAS devices present storage resources onto the LAN network that are shared by the client computer systems attached to the LAN. The Client Applicationare shared by the client computer systems attached to the LAN. The Client Applicationaccesses the Virtual storage resource without knowledge of the whereabouts of the accesses the Virtual storage resource without knowledge of the whereabouts of the Resources.Resources.

04/22/2304/22/23 1414

• The application File I/O access request are The application File I/O access request are handledhandled

by the client OS in the form of system calls.by the client OS in the form of system calls.

• The system calls are intercepted by an I/O The system calls are intercepted by an I/O redirectorredirector

layer determines if the accessed data is layer determines if the accessed data is part of the remote file system or the local part of the remote file system or the local attached file system.attached file system.

• The data is part of the remote file system, The data is part of the remote file system, the file director Passes the commands onto the file director Passes the commands onto the NFS protocol stack that maps the file the NFS protocol stack that maps the file access system calls into command message access system calls into command message for accessing the remote file for accessing the remote file

servers in the form of NFS or CIFS servers in the form of NFS or CIFS messages.messages.

• These remote file access messages are then These remote file access messages are then passed onto the TCP/IP protocol stack, passed onto the TCP/IP protocol stack, which ensures reliable transport of The which ensures reliable transport of The message across the network. The NIC driver message across the network. The NIC driver ties the TCP/IP stack to the NIC. The ties the TCP/IP stack to the NIC. The Ethernet NIC provides the Physical interface Ethernet NIC provides the Physical interface and MAC function to the LAN network.and MAC function to the LAN network.

04/22/2304/22/23 1515

In the NAS device, the NIC receives the Ethernet In the NAS device, the NIC receives the Ethernet Frames Carrying the remote file access commands. Frames Carrying the remote file access commands. The NICdriver Presents the datagram's to the TCP/IP The NICdriver Presents the datagram's to the TCP/IP stack.stack.

The TCP/IP stack recovers the original NFS or CIFS The TCP/IP stack recovers the original NFS or CIFS Messages sent by the client system. The NFS file Messages sent by the client system. The NFS file Access Handler processes the remote file commands Access Handler processes the remote file commands from the NFS/CIFS messages and maps the from the NFS/CIFS messages and maps the commands into file Access system calls to file commands into file Access system calls to file

system system of the NAS device.of the NAS device.

The NAS file system, The Volume Manager and disk The NAS file system, The Volume Manager and disk System device driver operate in a similar way as the System device driver operate in a similar way as the DAS file system, translating the file I/O commands DAS file system, translating the file I/O commands Into block I/O transfers between the Disk controllerInto block I/O transfers between the Disk controller/ HBA and the disk system that is either part of the / HBA and the disk system that is either part of the NAS device or attached to the NAS device NAS device or attached to the NAS device

externally.externally.

04/22/2304/22/23 1616

04/22/2304/22/23 1717

Merits of NAS Approach:Merits of NAS Approach:

Providing data access to clients and backing up data,NAS Providing data access to clients and backing up data,NAS devices handle tasks such as proxy, Firewall, tape backups devices handle tasks such as proxy, Firewall, tape backups and audio/Video streaming.and audio/Video streaming.

Advantage of Implementing NAS solutions on a network.Advantage of Implementing NAS solutions on a network.

Improved server Performance:Improved server Performance:

Data is stored separately from the server, the strain of file Data is stored separately from the server, the strain of file processing is eliminated from the server. As a result, the processing is eliminated from the server. As a result, the server only needs to process request from its clients.server only needs to process request from its clients.

Increased Reliability and data availability:Increased Reliability and data availability: NAS device operate independently of servers, even if a server NAS device operate independently of servers, even if a server

down data is available to the client through other serversdown data is available to the client through other servers

04/22/2304/22/23 1818

Easy Scalability:Easy Scalability:

NAS devices can be attached to a network during working hours, withoutNAS devices can be attached to a network during working hours, without having to interrupt the normal functions of a network. having to interrupt the normal functions of a network.

Easy Manageability:Easy Manageability:

Administering a NAS device is easy because it configures itselfAdministering a NAS device is easy because it configures itself dynamically after being connected to the network.dynamically after being connected to the network.

NAS device can be access remotely either with the help of NAS device can be access remotely either with the help of StandardStandard

Web browsers or Third-party management tools.Web browsers or Third-party management tools.

Support to heterogeneous networking Support to heterogeneous networking environmentenvironment

Transparent Backups:Transparent Backups:

Data stored on the NAS devices can be backed up without Data stored on the NAS devices can be backed up without affecting other serversaffecting other servers

04/22/2304/22/23 1919

Increased Network Productivity:Increased Network Productivity:

The implementation of NAS solutions increases the productivity The implementation of NAS solutions increases the productivity and the efficiency of the entire network.and the efficiency of the entire network.

Reliable access to the data at all times improves client Reliable access to the data at all times improves client productivity.productivity.

Servers show a marked improvement in their performance as theServers show a marked improvement in their performance as the CPU-intensive I/O activities are performed by the NAS devices.CPU-intensive I/O activities are performed by the NAS devices.

Implementation of the NAS device also simplifies the job of Implementation of the NAS device also simplifies the job of networknetwork

Administrators by allowing them to add additional storage to theAdministrators by allowing them to add additional storage to the network on-the-fly without having to bring down the entire network on-the-fly without having to bring down the entire

network.network.

Reduced TCO:Reduced TCO: By bringing down administrative and productivity costs, NAS By bringing down administrative and productivity costs, NAS

solutions result in a marked reduction TCO.Business can also solutions result in a marked reduction TCO.Business can also reduce expenditures on skilled IT staffs that would be required reduce expenditures on skilled IT staffs that would be required for less effective systems of Storagefor less effective systems of Storage

04/22/2304/22/23 2020

Demerits of NAS Approach:Demerits of NAS Approach:

NAS works well in small– to medium-sized networks, it can prove to beNAS works well in small– to medium-sized networks, it can prove to be highly insufficient in the case of large networks.highly insufficient in the case of large networks.

Excessive Network Traffic:Excessive Network Traffic: A request from a client is targeted at the server, which then passes it A request from a client is targeted at the server, which then passes it

on to the corresponding NAS device. The NAS device then returns the on to the corresponding NAS device. The NAS device then returns the requested data to the server. The server consequently forwards the requested data to the server. The server consequently forwards the data to the client. This is a long procedure and both the client/server data to the client. This is a long procedure and both the client/server interaction and server/NAS device interaction use network bandwidth.interaction and server/NAS device interaction use network bandwidth.

Slow Transactions :Slow Transactions : Although NAS devices function at high speeds, the response time to Although NAS devices function at high speeds, the response time to

client request can increase during speak hours when the number of client request can increase during speak hours when the number of clients requesting information is high.clients requesting information is high.

Increased Vulnerability:Increased Vulnerability: Because NAS device are directly attached to the network and can be Because NAS device are directly attached to the network and can be

easily accessed, they are vulnerable to malicious attacks. As a result easily accessed, they are vulnerable to malicious attacks. As a result there is a great chance that confidential business data can be there is a great chance that confidential business data can be compromisedcompromised

04/22/2304/22/23 2121

Storage Area NetworksStorage Area Networks

04/22/2304/22/23 2222

SAN provides block-orient I/O between the computer systems and the target disk systems.

SAN may use Fibre Channel or Ethernet (iSCSI) to provide connectivity between hosts and storage

SAN is often built on a dedicated network fabric that is separated from the LAN network to ensure the latency-sensitive block I/O SAN traffic does not interfere with the traffic on the LAN network

The SAN fabric ensures a highly reliable, low latency delivery of traffic among the peers.

SAN are optimized for high volume block oriented data

SAN support a board range of application including providing storage for NAS application.

I/O request to disk storage on a SAN are called “block I/O S”

04/22/2304/22/23 2323

SAN Software ArchitectureSAN Software Architecture

04/22/2304/22/23 2424

SAN software Architecture is same as the software Architecture SAN software Architecture is same as the software Architecture of DAS system, the key difference is that disk controller driver is of DAS system, the key difference is that disk controller driver is

replaced by either the Fiber channel protocol or the iSCSI/TCP/IPreplaced by either the Fiber channel protocol or the iSCSI/TCP/IP Stack that provides the transparent function for block I/O Stack that provides the transparent function for block I/O

commands to the remote disk system across the SAN Network.commands to the remote disk system across the SAN Network.

The block I/O SCSI commands are mapped into FC frames at the The block I/O SCSI commands are mapped into FC frames at the FC-4 layer.FC-4 layer.

The FC-2 and F C-1 layer provides the signaling and physical The FC-2 and F C-1 layer provides the signaling and physical transport of the frames VIA the HBA driver and the HBA transport of the frames VIA the HBA driver and the HBA hardware.hardware.

AS the abstraction of storage resources is provided at the block AS the abstraction of storage resources is provided at the block level, the application that access data at the block level can work level, the application that access data at the block level can work in a SAN environment.in a SAN environment.

SAN storage model, the operating system view storage SAN storage model, the operating system view storage resources as SCSI devices. Therefore, SAN infrastructure can resources as SCSI devices. Therefore, SAN infrastructure can directly replace DAS without significant changes to the operating directly replace DAS without significant changes to the operating system.system.

04/22/2304/22/23 2525

Fibre channel StructureFibre channel Structure

04/22/2304/22/23 2626

Merits of SAN Approach:Merits of SAN Approach:

• ScalabilityScalability Network PerformanceNetwork Performance Data AvailabilityData Availability Fast data Transfer RatesFast data Transfer Rates ReliableReliable Transparent backup and restoreTransparent backup and restore SAN support cross PlatformSAN support cross Platform SecuritySecurity Reduced TCOReduced TCO

04/22/2304/22/23 2727

Scalability :Scalability :Adding new storage resources to network dynamically. Storage Adding new storage resources to network dynamically. Storage device is not associated with any server, adding a new Storage device device is not associated with any server, adding a new Storage device doesn’t lead to adding a corresponding server. This is a boon in mask for doesn’t lead to adding a corresponding server. This is a boon in mask for the most Network administrators Because they have to manage fewer the most Network administrators Because they have to manage fewer devices. This brings down the TCO of the network.devices. This brings down the TCO of the network.

Network Performance: Network Performance: Network performance also improves with SANs. Server/storageNetwork performance also improves with SANs. Server/storageinteractions do not use network bandwidth, which reduce network trafficinteractions do not use network bandwidth, which reduce network trafficconsiderably. This is because bandwidth intensive bulk-data transfers suchconsiderably. This is because bandwidth intensive bulk-data transfers suchas backups and database updates ,occurs with the SAN as a result, traffic as backups and database updates ,occurs with the SAN as a result, traffic On the LAN, Which is attached to the SAN, is not affected and user canOn the LAN, Which is attached to the SAN, is not affected and user canContinue with normal work without having to feel the bandwidth pinch.Continue with normal work without having to feel the bandwidth pinch.so Server performance is improved. Servers become free from data I/O so Server performance is improved. Servers become free from data I/O Activities, which are highly CPU-intensive. As a result servers can process Activities, which are highly CPU-intensive. As a result servers can process Client response time. Client response time.

04/22/2304/22/23 2828

Data Availability :Data Availability :In a SAN setup, multiple servers share access to the same data In a SAN setup, multiple servers share access to the same data Simultaneously. If a server becomes unavailable, other server can Simultaneously. If a server becomes unavailable, other server can take over, which results in improved data availability to the clients and take over, which results in improved data availability to the clients and high failovers. This helps in eliminating data-accessibility problem that high failovers. This helps in eliminating data-accessibility problem that arise due to SPOF.arise due to SPOF.

Fast data Transfer Rates : Fast data Transfer Rates : The FC infrastructure , which forms the base of the SAN, guarantees fastThe FC infrastructure , which forms the base of the SAN, guarantees fastData transfer rates (from 100 Mbps to 1.0625Gbps). This data rate is faster Data transfer rates (from 100 Mbps to 1.0625Gbps). This data rate is faster than data exchange rates in LANs to which the SAN is connected. This isthan data exchange rates in LANs to which the SAN is connected. This isespecially beneficial in the case of E-commerce where fast data transactionespecially beneficial in the case of E-commerce where fast data transaction to online companies that are aiming to gain favor from user.to online companies that are aiming to gain favor from user.

Reliability :Reliability :SANs are based on Fibre channels and Switched Fibre technology and can SANs are based on Fibre channels and Switched Fibre technology and can be accessed from any where in the network, there is a low probability of abe accessed from any where in the network, there is a low probability of aSPOF also being separate from the primary networks, SANs are lessSPOF also being separate from the primary networks, SANs are lesssusceptible to data corruption. These factors make them highly reliable.susceptible to data corruption. These factors make them highly reliable.

04/22/2304/22/23 2929

Transparent backup and restore :

In a SAN Setup, the storage devices that needs to be backed- up are separate from the primary LAN. This externalization of storage makes Backup activities faster and transparent to the user who can continue their normal operation without feeling a bandwidth pinch. Similarly data can be restore quickly and easily while primary network still Operational.

SAN Supports Variety of cross Platform Data Sharing :

( Windows, UNIX, Linux, Macintosh, OS/390. and so on) and support Multiple protocols like TCP/IP and IPX. SANS supports storage Protocols such as Storage IP, Fibre Channel and Infini Band.

04/22/2304/22/23 3030

Security :Security :In a SAN setup Storage are not visible to users. So resources can be accessed only through network servers. Moreover SANs support

auditable Security mechanisms to prevent unauthorized access to the data. If

servers are Properly configured for secured access to storage resources, The probability of malicious, Unauthorized access can be reduced Substantially.

Reduced TCO :Reduced TCO :Finally, centralized management is far less expensive than the Finally, centralized management is far less expensive than the

traditional traditional model that consists of standalone servers and storage devices. model that consists of standalone servers and storage devices.

Improved Improved performance, high data availability and easy backups and restore also performance, high data availability and easy backups and restore also Contribute to a reduces TCO. Obviously SANs meet the requirement of Contribute to a reduces TCO. Obviously SANs meet the requirement of their development goals their development goals

04/22/2304/22/23 3131

THANK YOU