A brief overview of DAS, NAS and SAN data storage systems

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NAS, DAS, and SAN are different data storage methods, each with unique characteristics. They are not mutually exclusive - they can be mixed and used separately.

DAS (Direct-Attached Storage) is an external device or internal storage device connected directly, not via a common network, to a single server (sometimes to a cluster), PC or workstation. Most often connected via FC, SATA, eSATA, SAS, USB and Thunderbolt interfaces. De facto DAS is fast (if the interface is fast) local storage, accessible only to the device to which it is connected. The hard drive inside your PC is also a kind of DAS.

Modern external DAS devices have redundant power supplies, built-in cooling, disk controllers, and the ability to create RAID arrays to offload the main server controller.

DAS usage example: A video production company uses a DAS device (with its own power supply and cooling) to store and work with large files without copying. This DAS is connected via Thunderbolt directly to the workstation - without an intermediate switch. The editor gets fast access to data and high storage performance in real time while editing the video. But to access the video from other devices, the company uses NAS and cloud storage.

NAS (Network Attached Storage) is a specialized device or a dedicated server for storing files with a network connection. Sometimes even a NAS is made from a PC, but such a device loses to a specialized NAS server in terms of performance and/or availability and/or reliability. A NAS can have its own SHD or disk shelf (JBOD, just-a-bunch-of-disks). Yes, you can also connect a DAS to a NAS.

Typically, NAS is connected to main servers, workstations or PCs via Ethernet. Since NAS stores files, the connection protocols are file-based: SMB/CIFS, NFS, FTP, SFTP, HTTP, WebDAV, DC, BitTorrent, etc.

Example of NAS usage: The company has a network for centralized storage and file sharing between employees. All corporate information, documents, images and video files are stored on a NAS server. Each employee has quick and convenient access to data from anywhere on the network. All files are protected by access settings and encryption. Backups protect against data loss, and high-availability server technologies protect against downtime.

SAN (Storage Area Network) is not just a device, but an infrastructure solution for centralized or distributed data storage, sharing and management. SAN does not store files like NAS, but provides block storage. From a hardware perspective, it can look like this: servers + SDA + switches + patch cords + monitoring and management systems + backup systems + DAS and even NAS.

SAN provides high performance and flexibility, allows archiving, backup and recovery of data after failures. Ideal solution for large companies and complex infrastructures. Typically works with Fibre Channel, iSCSI, Fibre Channel over Ethernet (FCoE) and NVMe over Fabrics (NVMe-oF) protocols. Sometimes several protocols are used in parallel.

SAN example: A financial company uses a SAN to centrally store and process critical financial data (transaction records, customer accounts, and transaction history). SAN provides fast, scalable, and fault-tolerant storage that is layered across multiple servers for data sharing and processing. Fault tolerance is achieved by replicating data between different data centers and using RAID arrays to protect against disk failures. Scalability is achieved by easily integrating new storage and expanding existing storage.

All this guarantees quick access to financial transactions and compliance with strict security and data backup standards, which is critically important in the financial sector.

The importance of choosing between DAS, NAS and SAN for data storage in a company
NAS is usually a good option for small and medium-sized businesses because it is easier to set up and use. DAS is for local high-performance tasks, and SAN is for corporate and high-load environments that require high fault tolerance and performance to process large amounts of data. All of these can be used together, combined to solve different tasks in one infrastructure.

Data sharing.

• DAS: Suitable for a single server or application.
• NAS: Supports multiple users and applications via network protocols.
• SAN: Sharing data between multiple servers, ideal for large numbers of users and applications.

Productivity.

• DAS: High performance for individual servers.
• NAS: Average performance, suitable for shared file access, but not always ideal for applications with high performance requirements.
• SAN: High performance, especially when using good controllers and high-speed Fibre Channel, Ethernet, or any IB interfaces.

Scalability.

• DAS: Low scalability. Vertical is limited by the capabilities of the device chassis and interface bandwidth, and horizontal is limited by the number of connectors in the server/PC.
• NAS: Average scalability. There is clustering, storage expansion, but with increasing data volume there may be performance issues (if the system is not designed in advance with high load in mind).
• SAN: Highly scalable. Allows you to add storage devices and servers without interrupting the system. Distributed infrastructure allows you to distribute the load and increase system performance in real time.

Management complexity.

• DAS: Easy to install and configure, but each device needs to be serviced separately, which is problematic with a large number of servers and DAS.
• NAS: Relatively easy to manage due to network connectivity and centralized file access. However, careful management is required as you scale and increase the number of users (e.g. security settings, including access rights).
• SAN: More complex to set up and manage. Requires specialized administration skills. But the level of control and manageability is extremely high.

Investments.

• DAS: Low initial setup costs, but scaling means buying new devices, storage, and increased maintenance costs.
• NAS: Average cost, good price/performance ratio, but limited file storage.
• SAN: High initial costs due to hardware purchase and network infrastructure deployment. Requires skilled (read - highly paid) staff to maintain. But in the long run it is a cost-effective investment, especially for large companies.

Safety and reliability.

• DAS: Relatively high level of reliability as the storage is directly connected to the server, which means minimal points of failure. Security is also high as there is no network connection, so access to the server is required to access the data.
• NAS: High reliability, provided that data redundancy and points of failure (power supply, drives, etc.) are configured. Almost all NAS systems, except for simple home ones, support RAID arrays to protect against disk failures. High level of security, but requires proper configuration of the access control system and data encryption (since there is network access to the data).
• SAN: Maximum reliability and availability with proper and careful configuration. Automatic data backup and mirroring, encryption, RAID arrays, clustering can be implemented. For increased security, monitoring, access control, logging, and auditing are required.

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