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iSCSI is a storage area networking (SAN) protocol. Also known as iSCSI SAN storage, it defines the data transfer process between host and storage systems. Additionally, iSCSI enables small computer system interface (SCSI) data transportation from the iSCSI initiator to the storage target and vice versa, a process that takes place at the block level using TCP/IP networks.

Compared to the more traditional fiber channel (FC) SAN, iSCSI storage is cost-effective and does not require dedicated hardware such as an FC switch and FC host bus adapter (HBA). In fact, iSCSI SAN storage can be deployed on existing network hardware such as routers and fiber switches. iSCSI is also faster and more efficient than FC SAN as it is based on the block transfer standard.

iSCSI has two key components: the iSCSI initiator and the iSCSI target. The iSCSI initiator is a hardware or software component deployed at the server level to transmit requests and receive responses from the iSCSI target. Conversely, the iSCSI target is deployed at the storage level and provides the required storage space.

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NFS is an open-source networking protocol for distributed file sharing. This standard protocol is leveraged for data distribution and relies on TCP/IP for communication. Enterprises can use NFS on virtually any operating system or device.

In a nutshell, NFS enables users to remotely access les on servers without disrupting the user experience the files can be accessed seamlessly as if they are stored locally. Apart from this, NFS provides scalability and security.

First introduced in 1985, NFS was updated several times. The first version was built to link UNIX hosts and remote computers. NFSv2, which served the same purpose as version 1 but had added TCP/IP support, was released in 1989. NFSv3 was released in 1994, featuring enhanced networking support and increased eciency. Finally, the current version of the network le system is NFS Version 4 (NFSv4). This version is documented in RFC 7530 and focuses on security, performance, and data integration.

NFS is popular for several use cases. For instance, it is deployed in UNIX environments to share les between users and computers with read or write access. Think of a field professional with no fixed endpoint device this person can access the required les from different endpoints using NFS even though the files are not stored in the local system. This is possible because the les are stored on a central network server.

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Internet small computer system interface (iSCSI) is a SAN protocol that sets rules for data transfers between host and storage systems. On the other hand, network file system (NFS) is a distributed file system protocol that enables users to access les stored remotely, similar to how local storage is accessed.

iSCSI vs. NFS: Architectural Overview

Sources: TechTargetOpens a new window and BaeldungOpens a new window

Lets dive in and learn more about the key comparisons between iSCSI and NFS.

iSCSI works by transmitting block-level data between an iSCSI initiator (placed on a server) and an iSCSI target (placed on a storage device). Once the packet reaches the iSCSI target, it is disassembled, and the SCSI commands are separated by the protocol. This allows the storage to be visible using any operating system.

Unlike its alternatives (such as fiber channels), iSCSI can work on existing IP infrastructure without dedicated cabling. As a result, it can serve as a low-cost SAN option.

iSCSI can establish communications with arbitrary SCSI device types. This protocol is widely used by system administrators to set up servers for disk volume access on storage arrays. However, performance issues may arise if iSCSI is not deployed on a dedicated network or subnet.

The client-side may issue two types of requests: read requests and write requests. Read requests are issued when the client wants to read the data on the server. Write requests are issued to the server when the client computer needs to write over the existing data. The read and write requests are implemented using the standard read/write operations. The server computer completes the request by leveraging the corresponding protocol. The data is then returned to the client computer.

Data requests from NFS clients are transmitted through the NFS server. The server retrieves the requested data from the storage and transmits it back to the clients.

Shared le locking is a key software feature of NFS. Shared le access can be implemented by properly specifying both le locking and caching parameters. If the user fails to specify these parameters and le data is only retained in a host cache, all NFS storage clients use the same locking and caching parameters for mounted les.

In cases where multiple computers or threads attempt to access one le simultaneously, the shared file access feature may malfunction. The le locking mechanism was developed to improve the efficiency of shared le access functionality. Shared le access can be executed within a single host or among several hosts, with NFS being used for accessing the same le.

The iSCSI initiator is the host-based hardware or software component. Deployed on the server, this component enables data transmission to and from the storage array. The source array is also capable of serving as a data migration initiator among the storage arrays. The storage network can be created using standard Ethernet components for the software initiator. iSCSI initiators manage several parallel communication links to several targets at once.

The iSCSI target is the component deployed on the storage side. It essentially plays the role of a server that hosts storage resources and allows storage access. iSCSI targets are basically the storage resources within an iSCSI server. They generally represent hard disk storage and are usually accessed via Ethernet.

Targets are data providers and include tape libraries and disk arrays. They expose one or more SCSI logical unit numbers (LUNs) to specific iSCSI initiators. However, iSCSI targets are the logical entities within the context of enterprise storage. iSCSI targets manage several parallel communication links to several initiators.

Next comes the iSCSI HBA, similar to a fiber channel. It offloads computing responsibilities from the system processor. iSCSI HBA helps enhance server network and storage performance but can cost more than a standard Ethernet NIC.

Finally, the iSCSI iSOE can be a good alternative for iSCSI HBA, as it provides similar functionality at a lower cost.

NFS operations leverage three main components, which, logically speaking, reside at the three OSI model layers corresponding to the TCP/IP application layer.

The above three key components or subprotocols represent most of the NFS protocol. Apart from them, the protocol includes numerous other functions. Of these, the key ones are highlighted below.

A key advantage of iSCSI is its use of TCP/IP, which allows for long-distance IP routing without external gateway hardware. It also provides a large storage network environment and increased flexibility.

Standard Ethernet

Using Standard Ethernet by iSCSI means that the protocol does not require expensive components to be built and deployed.

Storage array

A large storage array for iSCSI targets can be either open-source software or commercial. Unique iSCSI targets are provided for numerous clients.

Security

Internet security protocol is leveraged to secure IP network traffic by encrypting and authenticating each data packet received.

RPC is available for servers as well as clients. It replaces the transport device interface for enhanced scalability and support.

Multiple port extensions support RPC ports that are easy to use at the client level and compatible with firewalls.

Firewall compatibility is a key advantage of NFS version 4 and uses TCP Port -2049 for service execution. This simplifies protocol usage across firewalls.

Finally, NFS is a kerberized file system interface and features additional Kerberos privacy, such as Krb5p, to support krb5, krb5i, and other existing Kerberos options.

iSCSI is primarily designed for Microsoft Windows.

This protocol facilitates block-level sharing, allowing connected devices to access and utilize storage resources at the block level, similar to a local hard drive.

In an iSCSI setup, the responsibility of managing the file system lies with the guest operating system. This means that the guest OS handles tasks related to the file system, such as organizing and managing files and directories.

With iSCSI, each volume on the block level can be accessed by a single client, ensuring dedicated access and control over the storage resources.

In iSCSI, the file system is implemented at the client level. This enables both data and metadata to be read and managed within the client file system.

Implementing iSCSI can be slightly challenging as it requires configuring hosts, storage options, virtual local area networks (VLAN), and other related settings to ensure proper functionality and integration with the system.

NFS can be used for Microsoft Windows, Linux, and UNIX operating systems, making it a versatile choice for cross-platform environments.

It facilitates file-based sharing, enabling clients to access and share individual files or directories rather than accessing storage at the block level.

In an NFS setup, the responsibility of managing the file system (such as organizing and managing files and directories on behalf of the clients) rests with the NFS server.

NFS allows files to be shared among multiple servers, providing a means for collaborative access and data sharing across server environments.

In NFS, the file system is implemented at the server level. This means the server maintains the file system, and clients access files within that shared file system.

NFS is a protocol known for its efficiency and streamlined design. It is considered a user-friendly choice as it is a shared protocol, making it easier for clients or users to implement and utilize it.

iSCSI is cost-effective in implementation, providing an economical network at the block level. The need for additional network devices is reduced as the protocol need not always use HBAs, distinct cabling, or specific storage devices.

iSCSI is also flexible as it runs on an internet protocol that does not limit the distance between the initiator and the target. This protocol fully leverages the interoperability advantages of Ethernet and TCP/IP. Plus, existing servers can be used several times for configuring iSCSI implementation.

iSCSI is known for swift data transfer even for larger volumes, as the protocol is normally configured for 10 gigabits per second Ethernet (GbE) infrastructure.

iSCSI is easy to deploy and manage, with the users who maintain it not requiring in-depth technical knowledge. The protocol is, therefore, conducive for development and disaster recovery too.

Finally, iSCSI features enhanced network security through identity authentication, physical and logical network isolation, confidentiality, and integrity.

NFS is secure as it uses strong authentication for protection against unauthorized access.

Users can share large les without breaking them down into smaller parts, and enterprises can collaborate across teams via NFS, thus enhancing productivity.

High scalability via data integration is a key benefit of NFS. The protocol can integrate local data with data from remote locations. Enterprises can, therefore, optimize their data centers and minimize costs by consolidating storage.

NFS provides speedy access to data by minimizing latency across wide area networks (WANs).

Like iSCSI, NFS is also suitable for disaster recovery and is used by organizations during disaster recovery planning. In case of a disaster, personnel can leverage NFS to create a virtualized remote copy of sensitive data.

Finally, NFS is secure and suitable for thwarting unauthorized access to data. It is also conducive for auditing and monitoring network activity remotely.

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In the realm of network storage, iSCSI and NFS are two well-known protocols.

iSCSI shines in block-based workloads, providing optimal performance for storage area networks (SANs), virtualization, and database applications, particularly in Windows and VMware environments. On the other hand, NFS excels in file-based workloads, offering high throughput and low latency, making it ideal for file-sharing and backup applications, particularly in Linux and UNIX environments.

While iSCSI boasts its own security features, NFS relies on the security mechanisms of the underlying network and file system. NFS scales easily by adding more servers and file systems, whereas iSCSI scales by adding more targets and logical unit numbers (LUNs). However, both protocols may encounter challenges when managing many connections, configurations, or devices.

NFS and iSCSI continue to evolve to meet the storage requirements of the modern world. They are integrating with cloud-based storage services, embracing software-defined storage solutions, and providing persistent storage for containerized applications, enhancing portability, performance, and scalability.

Despite their strengths, NFS and iSCSI face challenges in the network storage landscape. Compatibility issues, complex architectures, and competing protocols like SMB, CIFS, FCoE, NVMe-oF, and S3 can introduce interoperability problems, configuration errors, performance degradation, operational overhead, and security vulnerabilities.

Understanding the nuances of these two protocols and carefully assessing storage requirements will help users make an informed decision to ensure efficient and reliable network storage implementation.

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