FC SAN

Short for Fibre Channel Storage Area Network (SAN).

See also Fibre Channel and SAN.

Virtual SAN

Virtual SAN is a software-defined storage offering from VMware that enables enterprises to pool their storage capabilities and to instantly and automatically provision virtual machine storage via simple policies that are driven by the virtual machine.

VMware’s virtual storage area networking (SAN) solution also provides the ability to dynamically scale storage capacity and performance as needed, and exposes the underlying physical storage to the virtual machines through a policy-driven control pane.

VMware’s Virtual SAN, or VSAN, is currently in public beta release and is free for anyone to download.

 

SAN services

SAN services, short for Storage Area Network (SAN) services, is a technology used by businesses to obtain greater flexibility in their data storage. A Storage Area Network (SAN) provides raw storage devices across a network, and is typically sold as a service to customers who also purchase other services. SAN services may also be administered over an existing, local fibernetwork, and administered through a service subscription plan.

Learn more about SAN services on Datamation.
Learn more about storage networking on Enterprise Storage Forum.

Network Direct Attached Storage – NDAS

Network Direct Attached Storage (NDAS) is a proprietary digital storage technology that utilizes a Lean Packet Exchange (LPX) protocol to connect external digital storage devices to a network via Ethernet or USB. Unlike Network-Attached Storage (NAS), the LPX-based Network Direct-Attached Storage isn’t routable, so the storage hardware can’t be directly accessed via the Internet.

Originally developed by Ximeta in 2003 (and later marketed by IOCELL, which acquired Ximeta’s NDAS technology in 2011), Network Direct-Attached Storage is also different than Network-Attached Storage in that each client requires a software driver in order to access the NDAS storage hardware. The software driver enables any client on the network to directly control, use and share the NDAS device or devices.

Recommended Reading: What Is Enterprise Storage?

Advantages of Network Direct-Attached Storage

The purported advantages of Network Direct-Attached Storage are better performance, lower overhead (no operating system is needed in the device itself), enhanced security and simplified installation and ease of use. A variety of external digital storage devices can be used in Network Direct-Attached Storage form, including hard drives, optical drives, tape drive, flash drives and more.

NDAS vs. DAS, SAN and NAS

Network Direct-Attached Storage stands in contrast to Direct-Attached Storage (DAS) in that the latter refers to storage hardware that cannot be directly connected to a network, but they share the inability to be accessed via the internet. Network-Attached Storage (NAS) and Storage Area Networks (SANs), on the other hand, are more closely related to NDAS in that they both provide access to storage hardware on the network.

The primary difference between Network-Attached Storage and Storage Area Networks is that whereas NAS offers file-level storage reading, SANs are networks composed of storage devices that facilitate block-level storage. NDAS offers both file-level and block-level storage capabilities.

DAS – Direct Attached Storage

DAS is short for direct attached storage.

Direct attached storage (DAS), also called direct attach storage, is digital storage that is attached directly to a computer or a server. In other words, DAS isn’t part of a storage network. The most familiar example of DAS is the internal hard drive in a laptop or desktop PC. In practice, the phrase direct attached storage is used most often in reference to dedicated storage arrays attached directly to servers. It is used to distinguish DAS from networked storage arrangements, like SAN or NAS devices.

DAS Devices Explained

DAS can refer to a single drive or a group of drives that are connected together, as in a RAID array. In addition, DAS devices can be housed inside a PC or server (as is the case with internal hard drives) or outside the PC or server (as is the case with external hard drives and storage appliances). Multiple systems can use the same DAS device, as long as each PC or server has a separate connection to the storage device.

The primary benefits of DAS include simplicity and low cost. Installing networked storage systems, like NAS and SAN devices, requires more planning, as well as the purchase and deployment of network hardware, such as routers and switches, in addition to appropriate cabling and connections. By contrast, most PCs and many servers come with DAS already installed, and if you want to add more direct attached storage, generally all you need to purchase is a storage device and possibly a cable. Maintaining DAS is also very simple; by contrast, SAN and NAS solutions usually require management software and may require monitoring software as well.

The Difference Between DAS, SAN and NAS

In the early days of computing, DAS was the only type of storage available. In fact, the term direct attached storage didn’t come into use until much later when people needed a way to differentiate between traditional storage and SAN and NAS devices.

NAS (network attached storage) offers file-level storage for end users that are connected to a network. The advantage of NAS over DAS is that it simplifies file sharing among multiple users while potentially offering faster performance than a traditional file server.

SAN (storage area network) refers to a network of storage devices that provides block-level storage for servers in a data center. For large organizations with many servers, SAN offers better performance and flexibility than DAS, along with potential cost savings, although SAN hardware can be costly.

Many SAN and NAS devices can also be used as DAS devices. The difference lies in whether they are attached directly to a server or attached to a network via routers and switches.

Recommended Reading: What is Enterprise Storage?

Direct Attached Storage Implementation

Setting up a DAS device is generally very simple. When you purchase a PC, DAS is included in the form of the hard drive. If you would like to add more direct attached storage to a laptop or desktop, you can attach a plug-and-play external hard drive.

DAS is also included in many servers. Connecting additional DAS devices to servers is a little more complicated than adding DAS to a PC, but it is generally simpler than connecting SAN or NAS devices because it doesn’t require you to design a network or purchase hardware like routers and switches. Depending on the type of server, you may be able to add DAS in the form of additional drives in your existing server chassis. Other times, DAS sits in a separate chassis. You can also purchase DAS as storage appliances that you can connect directly to your servers. DAS deployment may require some configuration, but most IT workers can handle it on their own without outside consultants or specialized technical experts.

Using DAS is very easy. You simply save files as usual. Your operating system will allow you to view, rename, delete and perform other operations on the files on your DAS.

DAS Technology

DAS devices can utilize traditional spinning hard disk drives or solid state media. Hard disk drives (HDDs) are less expensive than solid state drives (SDDs) on a per gigabyte basis. However, they aren’t as fast as SDDs. The majority of DAS devices sold today use hard disk drives, although SSDs and hybrid devices are becoming more popular, particularly for applications where performance is paramount, such as Big Data analytics.

Conversely, SSDs offer the fastest performance, but they are also the most expensive. However, in recent years, they have become more affordable. In addition, because SSDs don’t have a spinning disk, they last longer and offer better reliability than HDDs. Many vendors now offer SSDs as an option on mid- to high-end servers for part or all of the storage capacity.

DAS devices can connect to PCs and servers via a variety of protocols, including SCSI, SAS, SATA, ATA, eSATA and Fibre Channel.

SAN fabric

The hardware that connects workstations and servers to storage devices in a SAN is referred to as a “fabric.” The SAN fabric enables any-server-to-any-storage device connectivity through the use of Fibre Channel switching technology.

storage management

The term storage management encompasses the technologies and processes organizations use to maximize or improve the performance of their data storage resources. It is a broad category that includes virtualization, replication, mirroring, security, compression, traffic analysis, process automation, storage provisioning and related techniques.

By some estimates, the amount of digital information stored in the world’s computer systems is doubling every year. As a result, organizations feel constant pressure to expand their storage capacity. However, doubling a company’s storage capacity every year is an expensive proposition. In order to reduce some of those costs and improve the capabilities and security of their storage solutions, organizations turn to a variety of storage management solutions.

Storage Management Benefits

Many storage management technologies, like storage virtualization, deduplication and compression, allow companies to better utilize their existing storage. The benefits of these approaches include lower costs — both the one-time capital expenses associated with storage devices and the ongoing operational costs for maintaining those devices.

Most storage management techniques also simplify the management of storage networks and devices. That can allow companies to save time and even reduce the number of IT workers needed to maintain their storage systems, which in turn, also reduces overall storage operating costs.

Storage management can also help improve a data center’s performance. For example, compression and technology can enable faster I/Os, and automatic storage provisioning can speed the process of assigning storage resources to various applications.

In addition, virtualization and automation technologies can help an organization improve its agility. These storage management techniques make it possible to reassign storage capacity quickly as business needs change, reducing wasted space and improving a company’s ability to respond to evolving market conditions.

Finally, many storage management technologies, such as replication, mirroring and security, can help a data center improve its reliability and availability. These techniques are often particularly important for backup and archive storage, although they also apply to primary storage. IT departments often turn to these technologies for help in meeting SLAs or achieving compliance goals.

Storage Management: Related Terms

Storage management is very closely related to Storage Resource Management (SRM). SRM often refers particularly to software used to manage storage networks and devices. By contrast, the term “storage management” can refer to devices and processes, as well as actual software. In addition, SRM usually refers specifically to software for allocating storage capacity based on company policies and ongoing events. It may include asset management, charge back, capacity management, configuration management, data and media migration, event management, performance and availability management, policy management, quota management, and media management capabilities. In short, SRM is a subset of storage management; however, the two terms are sometimes used interchangeably.

Storage management is also closely associated with networked storage solutions, such as storage area networks (SANs) and network-attached storage (NAS) devices. Because using SAN and NAS devices is more complicated than using direct-attached storage (DAS), many organizations deploy SRM software when they deploy their storage networking environments. However, storage management techniques like replication, mirroring, security, compression and others can be utilized with DAS devices as well as with SANs and NAS arrays.

Storage management is often used in virtualized or cloud computing environments.

Storage Management Implementation

Because storage management is such a broad category, it’s difficult to provide detailed instructions on how to install or how to use storage management technologies. In general, storage management technology can be deployed as software or it can be included in a hardware device. Storage management techniques can be applied to primary, backup or archived storage. Deployment and implementation procedures will vary widely depending on the type of storage management selected and the vendor. In addition, the skills and training of storage administrators and other personnel add another level to an organization’s storage management capabilities.

Storage Management Technology

The primary organization involved in establishing storage management standards is the Storage Networking Industry Association (SNIA). It has put forth several important storage specifications, including the Storage Management Initiative Specification (SMI-S) and the Cloud Data Management Interface (CDMI). SMI-S defines the attributes of storage hardware, such as Fibre Channel switches, Fibre Channel and iSCI arrays, NAS devices, tape libraries and host profiles. It also addresses storage management software issues, such as configuration discovery, provisioning and trending, security, asset management, compliance and cost management, event management and data protection. The CDMI specification provides standards for cloud storage services, enabling interoperability among various storage management solutions.

The work of the SNIA builds on previous work done by the Distributed Management Task Force (DMTF), which has also been involved in establishing storage management standards.

SAN – Storage Area Network

What is SAN?

Short for storage area network, SAN is a high-speed network of storage devices that also connects those storage devices with servers. It provides block-level storage that can be accessed by the applications running on any networked servers. SAN storage devices can include tape libraries and disk-based devices, like RAID hardware.

The main functions of a storage area network (SAN) includes the following:

• A high-speed network of storage devices.
• Connects the storage devices with servers.
• Can be accessed by applications on networked servers.
• Particularly helpful in backup and disaster recovery.
• Uses networking protocols to span longer distances geographically.
• SAN can also simplify some management tasks.
• Offers flexibility, availability and performance.

SAN Performance Compared to DAS

Organizations often choose to deploy a storage area network because it offers better flexibility, availability and performance than direct-attached storage (DAS). Because a SAN removes storage from the servers and consolidates it in a place where it can be accessed by any application, it tends to improve storage utilization. Storage utilization improvements often allow organizations to defer purchases of additional storage hardware, which saves money and requires less space in the data center.

Thanks to high-speed connections (usually Fibre Channel), SANs often provide better performance than DAS. Also, because SANs usually offer multiple connections to and from the data center’s servers, they also improve availability. In addition, separating the storage from the servers frees up the computing resources on the servers for other tasks not related to storage.

Image: What is SAN definition?

SANs Simplify Backup and Recovery

SANs are particularly helpful in backup and disaster recovery settings. Within a SAN, data can be transferred from one storage device to another without interacting with a server. This speeds up the backup process and eliminates the need to use server CPU cycles for backup. Also, many SANs utilize Fibre Channel technology or other networking protocols that allow the networks to span longer distances geographically. That makes it more feasible for companies to keep their backup data in remote locations.

Utilizing a SAN can also simplify some management tasks, potentially allowing organizations to hire fewer IT workers or to free up some IT workers for other tasks. It’s also possible to boot servers from a SAN, which can reduce the time and hassles involved in replacing a server.

Alternative Storage Options

Before the advent of SANs, organizations generally used direct-attached storage (DAS). As the name implies, direct-attached storage is directly attached to the server, residing either on the server or in a standalone storage device that is not part of a separate storage networking environment. Many smaller organizations continue to use DAS today because it offers lower upfront costs than deploying a SAN. However, for larger companies, the benefits of a SAN often outweigh the costs.

Sometimes people confuse the term SAN with the term NAS, which stands for “network-attached storage.” The key to distinguishing the two lies in the last term of each acronym: a SAN (storage area network) is an actual network, while NAS (network-attached storage) refers to a storage device, typically in an IP network. While SANs provide block-level storage for servers, a NAS device provides file-level storage for end users. For example, the mail application on your company servers might utilize a SAN to store all the messages, contacts and other data it requires; by contrast, an end user would use a NAS device to save files, such as word processing documents or spreadsheets. Operating systems see a SAN as a disk, while they see a NAS device as a file server.

Making things somewhat more confusing, some storage systems take a hybrid approach, offering some SAN capabilities as well as some NAS capabilities. It’s also possible to include NAS devices within a SAN.

How to Set Up a Simple SAN

To set up a simple SAN, you need only the following components:

• a SAN switch
• a storage device
• a server
• cables to connect the various elements together
• SAN management software

In most real-world settings, a SAN will include many different switches, storage devices and servers, and it will likely also include routers, bridges and gateways to extend the SAN over large areas and to connect to other parts of the data center network. The SAN’s topology will depend on its size and the needs of the organization.

The process of deploying a SAN requires several steps. First, you need to design your SAN, taking into account your current needs and future scalability requirements. Second, you’ll need to select a vendor or vendors to provide the hardware and software you’ll need, as well as any related services. Next, you’ll install the necessary hardware and then install and configure the software for managing your SAN. Deploying a SAN is a complicated process that often requires specialized knowledge and a great deal of planning, particularly if your SAN is very large.

SAN Standards and Technology

Several different industry groups have developed standards related to SAN technology. The most prominent is probably the Storage Networking Industry Association (SNIA), which promotes the Storage Management Initiative Specification (SMI-S), as well as related standards. The Fibre Channel Industry Association (FCIA) also promotes standards related to SAN and administers the SANmark Qualified Program.

Fibre Channel is currently the most widely used communication protocol for SANs, but it is by no means the only one. Some SAN networks rely on iSCSI communication, a mapping of SCSI protocol over TCP/IP. SANs can also use ATA over Ethernet (AoE), Fibre Channel over Ethernet (FCoE), ESCON over Fibre Channel, HyperSCSI and some other protocols.