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An investigation into the convergence of networking and storage solutions and comparison of the alternative networking/storage topologies

Name: Karan ChhabraStudent Number: 14111322Course: MSc in Cloud ComputingModule: Data Storage and Management

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Abstract:

This paper is based on the investigation inside the convergence of storage and networking solutions and also focuses on the comparison of alternate storage/networking topologies. This document provides a glimpse of the storage/networking topologies along-with the protocols used. The paper confers about the available topologies along with their merits and demerits.

Keywords: Direct Attached Storage (DAS), Network Attached Storage (NAS), Storage Area Network (SAN), Small Computer System Interface (SCSI), Internet Small Computer System Interface (iSCSI) and Fibre Channel (FC).

[I] Introduction:

In the modern world of Information and Communication Technology (ICT), the data is increasing at a rapid pace. The ICT industry has entered the era of BIG DATA and in order to support the increase in demand of storage for information services efficient and effective use of networking and storage resources is required. According to Siemon (2015), in last five years the size of a data record has tripled if not quadrupled, although the data has been structured, non-structured and semi-structured. According to a recent study at IBM, everyday 2.5 quintillion bytes of data are written, also the last two years have witnessed the creation of 90% of the global data. This huge increase in data has led to an exponential increase in the size of the databases. The most prominent challenge in front of the IT departments is to ensure the effective storage, access, protection and management of critical data.

As a result a huge opportunity is raised for the organizations to involve in the convergence and consolidation of storage and networking solutions. Also the organizations implement the Information Lifecycle Management (ILM) policies for efficient utilization of tiered storage and appropriate migration solutions for entities of data depending upon data characteristics. The structure of this paper is laid as follows. Section II discusses the Storage Networking topologies along-with their merits and de-merits. Section III describes the protocols associated in storage networking topology. The benefits of the convergence in network and storage are explained in Section IV and the final section concludes the paper.

[II] Storage Networking Topologies:

A topology is defined as a system in which the parts of a computer network are arranged or interrelated. According to Siemon (2015), Storage networking topologies are classified as follows: Direct Attached Storage (DAS), Storage Area Network (SAN) and Network Attached Storage (NAS).

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Direct Attached Storage (DAS):

In Direct Attached Storage the storage devices are locally attached to the servers locally and is achieved via a path of communication between the storage device and the server. A separate/dedicated path of communication is used between the storage device and the server and this path is distinct from the network cabling. An intelligent controller is used to provide access and only the server attached directly is able to access the storage. An extra storage unit is attached when an additional storage is required by the server. According to Somasundaram, G. & Srivastava, A. (2009) there are two types of Direct Attached Storage named Internal DAS and External DAS. In Internal DAS the host is connected to the storage device internally i.e. through a serial or a parallel bus. There is a limitation associated with the physical bus, for high speed connectivity the distance covered by the physical bus has to be small. Also most of the buses residing internally occupy huge space within the host and can support only a few amount of devices, whereas In External DAS the external storage device is externally connected to the server and also in many cases SCSI and FC protocols are used to carry the communication between storage device and the host. On comparing to Internal DAS, an External DAS supports large amount of devices and also overcome the limitation distance between the storage device and the host. A simple DAS diagram is explained in Figure 1.

Figure 1 DAS Diagram: Courtesy of Siemon (2015)

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Advantages:1. Direct Attached Storage incurs less implementation cost than in storage

networking.2. Direct Attached Storage can be configured and deployed rapidly and easily.3. The tasks for storage management are easy as the complete setup is managed by

using host based tools ex: Host OS.4. DAS is considered as the simplest solution as the amount of software elements

and hardware required is less and are also easy to operate.5. Security management in Direct Attached Storage is very much simplified.6. Highest bandwidth is offered by DAS along-with the fastest access rate.

Disadvantages:

1. Direct Attached Storage is not highly scalable.2. In DAS sharing of unused resources and data amongst servers is not possible.3. DAS doesn’t provides file or block level access to data.4. Limited number of ports in the storage device restricts the number hosts directly

connecting to the storage.5. Less I/O processing capacity due to limited availability of bandwidth.6. Service availability can be an issue when the capacities are reached.

Storage Area Network (SAN):

According to Racherla et al (2014) Fibre Channel Storage Area Networks are considered as a high performance approach for storage networking. A Fibre Channel SAN consists of FC ports which in turn are connected to FC switches. Therefore a Fibre Channel SAN is considered as a separate network for storage traffic. In large companies Fibre Channel SANs are used with large data stores. According to Siemon (2015) a networking model is applied by SAN to the storage in the data center. Cloudinfinit (2015) say that “SAN provides best of breed unified and integrated enterprise class storage in a tier-based performance through ISCSI/FC channel.” A diagram for Storage Area Network is shown in figure 2.

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Figure 2 SAN Diagram: Courtesy of Cloudinfinit (2015)

Advantages:1. Storage Area Network has high speeds.2. SAN is a pay per use model.3. The storage can be shared amongst multiple servers by means of SAN.4. SAN facilitate the companies with the ability to connect to servers and storage

which are dispersed geographically.5. It offers high security, high performance and high availability.6. The overall downtime and operational cost is reduced by SAN.

Disadvantages:

1. Implementation cost for SAN is high.2. Skilled labor is required to manage SAN.

Network Attached Storage (NAS):

The local Area Network is connected to storage devices in case of NAS. Various Network File Protocols (NLPs) are used by NAS in order to allow data access to many client systems which have different operating system. Somasundaram, G. & Srivastava, A. (2009) say “NAS uses network and file-sharing protocols to perform filing and storage functions.” The protocol used for data transfer is TCP/IP, NFS and CIFS for remote file service.Sacks (2001) discuss the use of NAS, usually in medium enterprises. A diagram for Network attached storage is described in figure 3.

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Figure 2 NAS Diagram: Courtesy of Somasundaram, G. & Srivastava, A. (2009)

Advantages:1. In NAS many servers can use same storage and share it with each other.2. Dedicated storage is not required in Network Attached Storage.3. Shared storage provided by NAS allows the servers to achieve more efficient

utilization.4. Less duplicate data as the data store is centralized in nature.5. Fast sharing of files by the clients.6. A NAS device provides a file serving and storage system which provides high

speed and high performance.

Disadvantages:

1. NAS can be a SPOF (Single Point of Failure) due to centralized database.2. Slower data transfer.

[III] Protocols associated in Storage networking Topologies:

According to Somsundaram & Srivastava (2009) some of the protocols associated with the topologies discussed above are SATA (Serial ATA), SCSI (Small Computer System Interface), FC (Fibre Channel), TCP/IP (Transport Control Protocol/Internet Protocol) and FCIP (Fibre Channel over IP).

SATA:

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SATA is a serial version of Integrated Device Electronics/Advanced Technology Attachment.

In SATA a direct link is formed which allows the bus to connect with each storage device.

SATA devices are pluggable as they can be added or removed even though the host is running.

SATA enforces connectivity to single device in order to eliminate the problems caused by port sharing.

A point to point connection is provided by SATA which is restricted to a distance of 1 meter.

A SATA enables a speed of 150 Mbps for data transfer and can be increased to 600 Mbps.

SCSI: SCSI is available for many interfaces out of which Parallel SCSI is known as one of

the most popular and oldest form of interface for storage. SCSI provides a SCSI command set that provides a high speed interaction

between a computer and a peripheral device. SCSI provides very high speeds of data transfer, utmost 320Mbps. SCSI has an edge over Integrated Device Electronics/Advanced Technology

Attachment as it can support 16 devices when compared to IDE/ATA which can support 2 devices.

SCSI has been available in iterations like SCSI1, SCSI2 and SCSI3. SCSI is used to connect hosts with hard disks and tapes.

FC: Fibre Channel acts as a fundamental construct for infrastructure of SAN. The increase in demand of high speed of data transfer led to the creation of

Fibre Channel. Fibre Channel runs on a very high speed network which is supported by optical

fibre and copper cables. The main aim to design Fibre Channel is to achieve very high speed of data

transfer. The data transfer speed range of Fibre Channel starts from 1 Gbps then to 2

Gbps, 4Gbps, 8Gbps, 10Gbps and 20 Gbps. The framework for Fibre Channel is highly scalable and 15 million nodes can

reside in a single Fibre Channel network. TCP/IP:

TCP/IP follows a two way process. TCP layer at one end (Client end) tries to manage the files at one end and TCP

layer at the other end (Server end) receives and reassembles the packets in a file.

FCIP:

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The encapsulated Fibre Channel data packets are transferred by a TCP/IP network.

The system at the receiver’s end de-encapsulates the encapsulated data packets. FCIP is considered as the cost effective method to blend IP infrastructure and FC

block data storage. TCP/IP protocol is used by FCIP. FCIP is used to connect the SAN islands and such interconnection is called FCIP

link. A fully merged Fibre Channel fabric is produced as a result of a successful FCIP

link between the two SAN islands.

[IV] Benefits of convergence in network and storage:

Since the evolution of networking and storage it has been really easy to see the transparency between them. According to Racherla et al (2014) Convergence is required in order to minimize the gap between the network and storage as the days when huge data centers with many and many rows are longer present. The convergence of storage and network has travelled a big expedition in order to mature faster. The major storage and network convergence are Internet Small Computer System Interface (iSCSI) and Fibre Channel over Ethernet (FCoE). Also server virtualization can be achieved along-side Fibre Channel storage and high Ethernet throughput. Convergence of storage and network requires a huge investment at the beginning but once this convergence is achieved it provides huge paybacks including: high reliability, high scalability, high throughput, less latency, easily manageable network infrastructure (high speed) and proper utilization of resources.

[V] Conclusion:

The future of Information and Communication Technology industry heavily lies in the hands of convergence. Convergence reduces the implementation costs and also provides a simpler deployment design. Storage and Networking convergence leads to the trails of small but highly efficient data centers. The convergence of the storage and networking will lead us to various important advancements such as: low electricity consumption, less complex data center design, highly scalable resources, high throughput, highly mobile data transfer and efficient utilization of hardware available.All these factors have contributed to the huge demand of storage and network convergence.

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References:

Cloudinfinit (2015), ‘SAN: Unified & Integrated Enterprise Class On-demand Storage.’ [Online]Available at: http://www.cloudinfinit.com/products/IaaS/cloud/storage/san [Accessed 8 April 2015]

Dabs (2015), ‘Network Attached Storage (NAS) Explained.’ [Online] Available at: http://www.dabs.com/learnmore/components-and-storage/network-attached-storage-(nas)-explained/ [Accessed 6 April 2015]

Racherla, S., Erdenberger, S., Rajagopal, H. & Ruth, K. (2014). ‘Storage and Network Convergence Using FCoE and iSCSI.’ [Online] Available at: http://www.redbooks.ibm.com/redbooks/pdfs/sg247986.pdf [Accessed 1 April 2015]

Siemon.com, (2015). ‘Data Center Storage Evolution: DAS, NAS, SAN, SAN over IP, FC, FCoE, iSCSI – Siemon’. [Online] Available at: http://www.siemon.com/us/white_papers/14-07-29-data-center-storage-evolution.asp [Accessed 4 April 2015].

Somasundaram, G. & Srivastava, A. (2009), ‘Information Storage and Management.’ Wiley Publishing, 2009. [Online] Available at: http://www.mikeownage.com/mike/ebooks/Information%20Storage%20and%20Management.pdf [Accessed 4 April 2015].

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