Storage Area Network
A data center built for a small business would be fine using a DAS or a NAS since there are now devices that provide terabytes of capacity and more capacity can be added by simply installing additional NAS storage devices. However, if that business grew into a large enterprise, its servers would need to accommodate a lot more data than DAS and NAS could hold.
A SAN (Storage Area Network) is one or many block-level storage devices clustered together that are attached to a high-speed network and that applications running on the servers, can connect in order to access the data. A characteristic of a SAN is that even though the storage is in another physical location, to the server, it looks and acts as if it was attached as a DAS.
A SAN requires that servers trying to connect to it also have certain protocols. Because a SAN requires a high-speed connection, faster protocols such as iSCSI, Fiber Channel (FC), and more recently Fiber Channel over Ethernet (FCoE) are used to transmit data at higher speeds on the TCP/IP network (internet).
This ability for storage to be shared outside of a local network makes a SAN an efficient storage type for larger companies whose employees need to access stored data from more than one location. Because a SAN requires higher speeds and a wider network area, it can be more expensive to set up but the ability to modify the size of the storage from anywhere at any time, called scalability, outweighs the costs for big organizations.
One way to understand the difference between a NAS and a SAN is that NAS is storage that connects to a network, and a SAN is a network of storage that servers can connect to. Also, a NAS manages storage as a file system directly while SAN storage devices do not, and it is the server’s operating system that is responsible for creating the storage file system. This may not seem important from a user’s standpoint; however, it affects the speed at which data is processed since a device that does not have to worry about filing its own data will run faster and be more efficient, which is important for overall data center efficiency.
Storage Protocols
Many types of storage protocols are available for configuring data center storage. The most efficient protocol for a particular data center depends on factors such as the size of the data center, types of servers used, and available budget. For example, some protocols ensure faster data transmission speeds but cost more to implement. Configuring storage with protocols that match the amount of data traffic a data center wants to handle can increase efficiency and ensure data gets to customers.
The following table lists common storage protocols and which storage configurations they are applied to,
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Protocol
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Application
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SCSI (Small Computer System Interface)
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Medium-sized blade servers, Enterprise servers, DAS
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SATA (Serial Advanced Technology Attachment)
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Small-sized tower server, DAS
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eSATA (external SATA)
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Small-sized tower server, DAS
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SAS (Serial Attached SCSI)
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Medium-sized blade servers, Enterprise servers, DAS
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FC (Fiber Channel) (single-mode) (SMF)
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Enterprise servers, SAN
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FC (Fiber Channel) (multi-mode) (MMF)
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Enterprise servers, SAN
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FCoE (Fiber Channel over Ethernet)
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Enterprise servers, SAN
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iSCSI (Internet Small Computer System Interface)
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Enterprise servers, NAS
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