SAN vs NAS - What’s the difference?
Compare and Contrast SAN and NAS
SAN (Storage Area Network) and NAS (Network-Attached Storage) are two acronyms frequently tossed around the data storage world. But what exactly are they, and more importantly how do they differ?
To start, understand that both NAS and SAN were developed to solve the problem of making stored data available to many users at once. But while each of them provides dedicated storage for a group of users, they couldn’t be more different in their approach to achieving this. Continue reading below for a brief comparison:
SAN: Dedicated Storage Network
Definition of SAN (Storage Area Network)
A storage area network (or storage network) is a dedicated, high-speed/high-performance storage device network that transfers block-level data between servers and storage devices. Unlike NAS it’s built from a combination of servers and storage over a high speed, low latency interconnect, and is more expensive and complex to set up and manage.
The basic idea of a SAN is simple: Put storage devices on a separate high-speed network, where they can be directly accessed by multiple servers or workstations, and managed as a centralised storage pool.
An essential function of a SAN is to permit storage devices, like disk arrays or tape libraries, to communicate not only with each other but also with server systems so that devices appear to the OS as direct-attached storage. In this way SAN facilitates universal connectivity, linking many computers to many storage devices, and enabling devices and data to be shared.
Use: Because it’s considerably more complex and expensive than NAS, SANs are used by large enterprises within data centres or virtual computing environments, and require administration by an IT staff.
Benefits of SAN
The primary strength of SAN is that it allows simultaneous shared access to shared storage that becomes faster with the addition of storage controllers:
- Extremely fast data access with low latency
- Relieves stress on a Local Area Network (LAN)
- Can be scaled up to the limits of the interconnect
- OS level (“native”) access to files
Limitations of SAN
The challenges of SAN lie solely in the cost and administration requirements. SAN implementation is complex, and dedicating and maintaining both an Ethernet network and Fibre Channel network can require a considerable investment.
NAS: LAN Storage Appliances
Definition of NAS (Network-Attached Storage)
A NAS is a computer connected to a network that provides file-based data storage services to other devices on the network. Unlike SAN, it’s a single storage device (maintaining its own IP address) that serves files over Ethernet and is relatively inexpensive and easy to set up.
The basic idea of NAS is simple: Attach special-purpose storage appliances to the LAN, which can be shared by application servers or workstations on the network.
Use: A NAS is frequently the next step up for a home office or small business that’s using external hard drives or direct attached storage, which can be especially vulnerable to drive failure. The move up to NAS is typically driven by the desire to share files locally and remotely.
Benefits of NAS
The primary strength of network-attached storage is how simple it is to set up and deploy:
- Relatively inexpensive
- A self-contained solution
- Ease of administration
- 24/7 and remote data availability
- Wide array of systems and sizes to choose from
- Automatic backups to other devices and the cloud
Limitations of NAS
The weaknesses of NAS are in the areas of scalability and performance. As more users require access, the server may not be able to keep up. The other weakness is related to the nature of Ethernet itself. By design, Ethernet transfers data from one place to another by dividing the source into a number of segments called packets; depending on existing network traffic, any of those packets could be delayed or sent out of order, or the file might not be available to the user until all of the packets arrive and are put back in order.
SAN vs NAS: A Summary
| SAN | NAS |
|---|---|
| More expensive (Due to Fibre Channel hubs) | Less expensive |
| Often used in larger professional and enterprise environments | Often used in homes and SMBs |
| Requires more administration | Easier to manage |
| Servers access data as if it were a local hard drive | Data accessed as if it were a network-attached drive |
| High speed using Fibre Channel | Speed dependent on local TCP/IP Ethernet network |
| Fibre Channel, iSCSI, FCoE | SMB/CIFS, NFS, SFTP, and WebDAV |
| Can add more storage controllers, or expanded storage arrays, allowing SAN admins to scale performance, storage, or both. | Lower-end NAS not highly scalable; high-end NAS scales to petabytes using clusters or scale-out nodes |
| Requires dedicated Fibre Channel connections for clients, servers, and storage, and often a separate, dedicated Ethernet network for file request traffic. | Simply connects to your existing Ethernet |
| Fault tolerant network and systems with redundant functionality | Entry level systems often have a single point of failure, e.g. power supply |
| Behavior is more predictable in controlled, dedicated environments | Subject to general Ethernet issues |
| A place from which to archive files not immediately needed | Need a central place from which to back up or sync user files |
Yes, SAN and NAS have a lot in common. Both are network-based storage solutions created to address the obstacle of providing shared storage. But from a user perspective, the biggest difference between them is that SAN-connected disks appear to the user as local drives, while NAS devices deliver shared storage as network mounted volumes. At the end of the day, choosing which one to implement within your organisation comes down to deciding which network criteria are most important to you.
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