DAS, NAS, and SAN are acronyms representing the 3 main types of storage available for servers. Each has its own benefits and weaknesses.
Direct attached storage arrays are disks that are connected to a server via its PCI bus through a host bus adapter (HBA). This can be anything from an onboard SATA controller to a Fiber HBA. The drives can either be located in the server itself, in a separate chassis, or connected to the server via a host bus adapter.
Benefits:
- Speed – very fast communication with the server. Moves data at the block level, so it good for database applications
- Cost – most of the cost is in the disks, overall its not very expensive
Drawbacks:
- Expandability – you are limited by the amount of space in a given chassis and it is fairly expensive to daisy chain to another chassis
- Sharing – you cannot easily share the data in this configuration, usually 1 server will only have access
Common Uses:
- Primary server storage
- OS Boot disks
- Databases
- Video streaming
NAS (Network Attached Storage)
NAS is an appliance that sits on the network and serves files to other servers and users on the network. In essence it is just a server that has been optimized for file serving. A NAS box runs an OS, usually Linux or Windows Storage Server.
Benefits:
- Cost – Less expensive than SANs, uses existing network bandwidth
- Sharing – Allows you to share files among many individual servers
Drawbacks
- Speed – you are communicating using existing Ethernet bandwidth and limited by its throughput. Data is moved at the file level, so it is not a good choice for databases
- Expandability – Although you may be able to add more drives to a NAS box, you are still limited by the capacity of that unit. If you need to grow beyond that, you need to add another NAS box
Common Uses
- File storage
- Backup (disk to disk)
- Paperless office migration (digital radiology, legal documents, etc.)
A SAN is an architecture where your storage sits on its own network, which can be accessed by multiple servers. It uses either Fibre channel or iSCSI protocols to move data and requires a separate switching structure to your standard network traffic.
Benefits
- Speed - SANs can move data much faster than NAS units, and they use their own bandwidth. Data is moved at the block level, so SANs can handle databases quite well
- Expandability - Most SAN solutions have the ability to easily share storage capacity among servers and to scale that capacity relatively easily
Drawbacks
- Cost - Because you need to invest in the network infrastructure, as well as the storage units, SANs are the most expensive solution. iSCSI technology is helping to significantly reduce SAN costs because you can use Ethernet switches, controllers, and cabling, instead of Fibre Channel-based infrastructure
Common Uses
- Enterprise storage (large networks that have many servers and can afford it)
- Clustering (needed to be able to share data)
Technology Section
High Performance Computing (HPC)
| This site made possible
by support from: |
 |
 |