NAS, DAS, and SAN are different data storage methods, each with unique characteristics. They are not mutually exclusive - you can mix them, you can use them separately.
DAS (Direct-Attached Storage) is an external device or internal drive connected directly, not through a public network, to a single server (sometimes to a cluster), PC or workstation. They are most often connected via FC, SATA, eSATA, SAS, USB and Thunderbolt interfaces. De facto DAS is a fast (if the interface is fast) local storage available 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 data access and high performance storage in real-time while editing video. But the company uses NAS and cloud storage to access videos from other devices.
NAS (Network Attached Storage) is a specialized device or custom server for storing files with a network connection. Sometimes even a NAS is made from a PC, but such a device loses to a dedicated NAS server in terms of performance and/or availability, and/or reliability. A NAS can have its own JBOD or just-a-bunch-of-disks (JBOD). Yes, you can connect a DAS to the NAS.
Typically, NAS are connected to main servers, workstations or PCs via Ethernet. Since the NAS stores files, so do the file connection protocols: SMB/CIFS, NFS, FTP, SFTP, HTTP, WebDAV, DC, BitTorrent, etc.
NAS usage example: A company has a network for centralized storage and sharing of files between employees. All corporate information, documents, images and video files are stored on the NAS server. Each employee has quick and convenient access to data from any point of the network. All files are protected by access and encryption settings. Data loss is protected by backup, and high-availability server technologies prevent downtime.
SAN (Storage Area Network) is not just a device, but an infrastructure solution for centralized or distributed data storage, exchange and management. A SAN does not store files like a NAS, but provides block storage. From a hardware point of view, it can look like this: servers + SZD + switches + patch cords + monitoring and management systems + backup systems + DAS and even NAS.
SAN provides high performance and flexibility, enabling data to be archived, backed up and restored after failures. An ideal solution for large companies and complex infrastructures. Typically works with Fiber Channel, iSCSI, Fiber 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 mission-critical financial data (transaction records, customer accounts, and transaction history). A SAN provides fast, scalable, and fault-tolerant storage that is spread across multiple servers for data sharing and processing. Fault tolerance is achieved by data replication between different data centers and the use of RAID arrays to protect against disk failures. Scalability - due to the easy integration of new repositories and the possibility of expanding old ones.
All this guarantees fast access to financial transactions and compliance with strict security and data backup standards, which is critical in the financial sector.
The importance of choosing between DAS, NAS and SAN for enterprise data storage
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 tasks with high performance, and SAN is for corporate and high-load environments that require high fault tolerance and performance to process large volumes of data. All this can be used together, combined to solve various tasks in the same infrastructure.
Data sharing.
- DAS: Suitable for a single server or application.
- NAS: Supports multiple users and applications over network protocols.
- SAN: Data sharing between multiple servers, ideal for large numbers of users and applications.
Productivity.
- DAS: High performance for individual servers.
- NAS: Average performance, suitable for general file access, but not always ideal for applications with high performance requirements.
- SAN: High performance, especially when using good controllers and high-speed Fiber Channel, Ethernet or any IB interfaces.
Scalability.
- DAS: Low scalability. The vertical one is limited by the capabilities of the device case and the bandwidth of the interface, and the horizontal one is limited by the number of connectors in the server/PC.
- NAS: Medium Scalability. There is clustering, storage expansion, but with an increase in the volume of data, there may be performance problems (if the system is not designed in advance with a high load).
- SAN: High scalability. Allows you to add DBS and servers without interrupting the system. Distributed infrastructure allows you to distribute the load and increase the performance of the system in real time.
Management complexity.
- DAS: Simple 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 with network connectivity and centralized file access. But when scaling and increasing the number of users, careful management (for example, security settings, including access rights) is required.
- SAN: More complex to configure and manage. Specialized administrative skills are required. But the level of control and manageability is extremely high.
Investments.
- DAS: Low initial setup costs, but scaling means buying new devices, storage, and maintenance.
- NAS: Average costs, good value for money, but limited in file storage.
- SAN: High initial costs due to hardware purchase and network infrastructure deployment. Qualified (read - highly paid) staff is needed for maintenance. But in the long run, it is an economically profitable investment, especially for large companies.
Safety and reliability.
- DAS: Relatively high level of reliability, because the storage is directly connected to the server, and this is a minimum of points of failure. Security is also high as there is no network connection and therefore access to the server is required to access the data.
- NAS: High reliability with configured data redundancy and duplication of points of failure (BZ, drives, etc.). Almost all NAS systems, except for simple home ones, support RAID arrays to protect against disk failures. A high level of security, but the correct configuration of the access control system and data encryption is required (since there is network access to the data).
- SAN: Maximum reliability and availability with proper and careful configuration. You can implement automatic data backup and mirroring, encryption, RAID arrays, clustering. Enhanced security requires monitoring, access control, logging, and auditing tools.
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