What is network-attached storage?
Network-attached storage (NAS) is a file-level storage architecture that makes stored data more accessible to networked devices. NAS is 1 of the 3 main storage architectures—along with storage area networks (SAN) and direct-attached storage (DAS). NAS gives networks a single access point for storage with built-in security, management, and fault tolerant capabilities.
How does NAS work?
Preconfigured storage software is installed on dedicated hardware. Known as a NAS box, NAS unit, NAS server, or NAS head, this hardware is essentially just a server containing storage disks or drives, processors, and random-access memory (RAM).
The main differences between NAS and general-purpose server storage lies in the software. NAS software is deployed on a lightweight operating system (OS) that’s usually embedded in the hardware. General-purpose servers have full OSs that send and receive thousands of requests every second—a fraction of which may be related to storage—while a NAS box sends and receives only 2 types of requests: data storage and file sharing.
A NAS box is formatted with data transfer protocols, which are standard ways of sending data between devices. These protocols can be accessed by clients through a switch, which is a central server that connects to everything and routes requests. Data transfer protocols basically let you access another computer’s files as if they were your own.
Networks can run multiple data transfer protocols, but 2 are fundamental to most networks: internet protocol (IP) and transmission control protocol (TCP). TCP combines data into packets before they’re sent through an IP. Think about TCP packets as compressed zip files and IPs as email addresses. If your grandparents aren’t on social media and don’t have access to your personal cloud, you have to send them vacation photos via email. Instead of sending those photos 1-by-1, you can bundle them into zip files before sending them over. In similar fashion, TCP combines files into packets before they’re sent across networks through IPs.
The files transferred across the protocols can be formatted as:
- Network File Systems (NFS): This protocol is regularly used on Linux and UNIX systems. As a vendor agnostic protocol, NFS works on any hardware, OS, or network architecture.
- Server Message Blocks (SMB): Most systems that use SMB run Microsoft Windows, where it’s known as “Microsoft Windows Network.” SMB developed from the common internet file sharing (CIFS) protocol, which is why you might see it referred to as the CIFS/SMB protocol.
- Apple Filing Protocol (AFP):A proprietary protocol for Apple devices running macOS.
- Scale-out capacity: Adding more storage capacity to NAS is as easy as adding more hard disks. You don’t have to upgrade or replace existing servers, and new storage can be made available without shutting down the network.
- Performance: Because NAS is dedicated to serving files, it removes the responsibility of file serving from other networked devices. And since NAS is tuned to specific use cases (like big data or multimedia storage), clients can expect better performance.
- Easy setup: NAS architectures are often delivered with simplified scripts, or even as appliances preinstalled with a streamlined operating system—greatly reducing the time it takes to set it up and manage the system.
- Accessibility: Every networked device has access to NAS.
- Fault tolerance: NAS can be formatted to support replicated disks, a redundant array of independent disks, or erasure coding to ensure data integrity.
NAS vs clouds
NAS by itself is not a cloud. Clouds are IT environments that abstract, pool, and share scalable resources across a network. NAS can be an important part of a cloud environments, particularly when cloud providers deliver storage to clients as part of an Infrastructure-as-a-Service (IaaS) agreement.
Comparing storage types
Storage area networks
A storage area network (SAN) provides block storage. Block storage splits storage volumes—like hard disks, virtual storage nodes, or pools of cloud storage—into smaller volumes known as blocks, each of which can be formatted with different protocols. For example, 1 block can be formatted for NFS, another can be formatted for AFP, and a third can be formatted for SMB. This gives users more flexibility, but also makes navigating the blocks harder since they’re bundles data together using arbitrary classifications.
Direct-attached storage (DAS) is storage that’s directly attached to a single computer. It’s not networked and so can’t easily be accessed by other devices. DAS was the precursor to NAS. Each DAS device is managed separately, while a NAS box manages everything. The most common example of DAS is a single computer’s hard drive. In order for another computer to access files on that drive, it must be physically removed from the original computer and attached to the new one, or a user must set up some sort of connection between the 2 devices—at which point the lines between DAS and NAS become a little blurry.
Software-defined storage (SDS) is storage management software that operates independently of the underlying hardware. That means it’s possible to install SDS on a NAS box, which allows the hardware to be tailored to specific workloads. With SDS installed, storage hardware can be clustered so multiple servers can operate as a single system for a specific purpose. For example, 1 server cluster can be configured to hold user directories and NFS/CIFS folders, while another is configured for block storage so it can hold photos and multimedia. Some NAS/SDS solutions can even consolidate and deliver more than a petabyte of data in 30 minutes or less.
Source : Network Attached Storage