When it comes to network storage solutions, NFS (Network File System) and iSCSI (Internet Small Computer System Interface) stand out as two prominent contenders. Both protocols have been here for years and offer great benefits for users. While both serve the purpose of facilitating storage access over a network, they differ in their architecture, performance characteristics, and suitability for various applications.

Choosing between either of the two will depend on several factors like performance, caching, reliability, and security. This article dissects NFS and iSCSI sharing protocols, including their definitions and features to determine which is the best choice for virtualization.

What is NFS?

NFS (Network File System) is a networking protocol that allows administrators to share file systems with other remote servers. It is commonly used in UNIX and Linux environments to store VM disk images and files over TCP/IP networks. NFS is widely used for file sharing, backup, and data analysis applications, especially in Linux and Unix environments. NFS was first introduced in 1984 by Sun Microsystems and has been updated several times over the years. The current version is the NFS version 4 (NFSv4).

What is iSCSI?

iSCSI (Internet Small Computer System Interface) is a transport protocol for small computer system interface (SCSI) over IP networks, It is also a storage area networking (SAN) protocol that facilitates data transfer between the client and server. The iSCSI has two components: the initiator and the target. The client (iSCSI initiator) creates the request while the server (iSCSI target) is configured to receive a response. IBM and Cisco developed the iSCSI protocol in 1998 and released the first draft in 2000.

Comparing NFS and iSCSI

Here is an in-depth comparison between NFS and iSCSI features:

  • Protocol Type:

NFS is a file-sharing protocol while iSCSI is a block-level protocol. Usually, the block-level protocol offers better benefits like efficiency and high performance.

  • Load Balancing:

Multipathing helps in balancing the load between the server and storage when one network path fails or overloads. Hence, storage connections can be more reliable and efficient.  In NFS, multipathing happens by configuring multiple network interfaces on both the server and storage. The interfaces will then be integrated into a single logical interface, allowing you to access a single NFS interface from multiple IP addresses. iSCSI creates multiple paths by configuring multiple networks at the VMkernel network adapter level. The initiator can then manage these connections using multipathing software or features that have been built into the operating system.

  • Performance:

iSCSI performs better for high-throughput and low-latency applications thanks to its block-level access. But its CPU load on the client host is higher. On the other hand, NFS doesn’t perform as well as iSCSI but it offers smoother performance. It features slightly higher latency because of its file-level access. Generally, you can improve iSCSI and NFS network performance using jumbo frames.

  • Caching:

NFS operates at the file level using strategies like write-behind caching and read-ahead caching. NFSv4 supports asynchronous data writes, but metadata updates are synchronous. Caching mostly occurs at the block level in iSCSI. After writing or reading an iSCSI volume, the operating system may cache frequently accessed blocks in memory to reduce latency and speed up access. The file system in iSCSI uses asynchronous metadata update which is less reliable compared to the synchronous method.

  • Ease of configuration:

Configuring iSCSI may be more difficult than NFS. However, it runs on different operating systems, making it flexible. It also transfers data over an IP. Hence, there’s no limit between the initiator and the target. NFS is easier to use and configure, and it may even be used out of the box. Although NFS is built for Linux, you can also use it on other operating systems when you install the necessary packages.

  • Reliability:

Both protocols are reliable, using TCP/IP for reliable data transfer. It possesses features like error detection, correction, and TCP retransmission. iSCSI also supports multipathing, making it more reliable by producing redundant network paths to prevent data loss. However, while NFS also relies on TCP/IP networks, it may not offer the same level of fault tolerance and redundancy as iSCSI. These features are crucial for advanced virtualization.

  • Security:

ISCSI and NFS offer high-level security through different means. iSCSI doesn’t encrypt data, but it uses a name and password for authentication during data sharing. iSCSI also features security systems through identity authentication, integrity, and confidentiality. On the other hand, NFS also doesn’t provide encryption. It uses host-based authentication. You have to define the host IP address before you can access the shared file.  NFS is also secure for protecting against unauthorized access to data.

  • Scalability:

iSCSI protocol is scalable, allowing for storage growth and expansion. Its block-level access allows for greater control over storage volume. NFS offers simple storage management, ensuring efficient scalability.  NFS also offers speedy access to data by reducing latency across wide-area networks (WANs). However, you must note that both protocols create room for scalability. But factors like network architecture may affect how scalable they are.

Which is Better for Virtualization?

Choosing between iSCSI and NFS for virtualization mainly depends on your unique needs. However, when comparing based on crucial factors like performance, iSCSI offers superior performance and flexibility. Hence, it’s the best choice for high virtualization workloads and performance-critical applications. iSCSI also has good control over storage resources, leading to effective management and allocation. So iSCSI is your go-to for heavy-duty virtualization and overall better performance. You can use NFS if you prioritize simplicity and easy use.


iSCSI and NFS are relevant protocols for virtualization. While iSCSI is a block-level storage protocol, NFS operates at the file level. Each protocol has its benefits and drawbacks. Comparing both protocols shows that iSCSI offers better performance and flexibility than NFS. While it’s the better option, your choice will depend on your needs. If you need a simple protocol, NFS is a great choice. However, for more sophisticated use and intensive virtualization workload, iSCSI is the best option.

text written by:

Grzegorz Pytel, Presales Engineer at Storware