SAN
- (The University of Chicago, Alvin Wei-Cheng Wong)
- Storage Network Architecture
A storage area network (SAN) is the most common storage network architecture used by enterprises for mission-critical applications that need to deliver high throughput and low latency. A rapidly growing segment of SAN deployments leverages all-flash storage for its high performance, consistently low latency, and lower total cost compared to spinning disk. By storing data on centralized shared storage, SANs enable organizations to apply consistent methods and tools for security, data protection, and disaster recovery.
A SAN is block-based storage that utilizes a high-speed architecture that connects servers to their logical disk units (LUNs). A LUN is a series of blocks presented from a shared storage pool and presented to a server as a logical disk. The server partitions and formats these blocks (usually using a file system) so that it can store data on the LUN as if it were on local disk storage.
SANs account for about two-thirds of the entire networked storage market. They are designed to eliminate single points of failure and make SANs highly available and resilient. A well-designed SAN can easily withstand multiple component or device failures.
- How Does SAN Storage Work?
A SAN consists of three distinct layers: host, fabric, and storage.
- The host layer. The host tier consists of SAN-connected servers running enterprise workloads that require access to storage, such as databases. A SAN host uses a host bus adapter (HBA), a separate network adapter dedicated to SAN access, to interface with the server's operating system. This allows workloads to use the operating system to pass storage commands and data to the SAN and its storage resources.
- The fabric layer. The fabric layer includes the cabling and network devices that make up the network fabric that interconnects SAN hosts and storage. SAN network devices can include SAN switches, gateways, routers, and protocol bridges. The fabric layer provides more redundancy over conventional networks by providing multiple alternate paths from the host to storage across the fabric. This means that if one path goes down, the SAN can use an alternate path to communicate.
- The storage layer. The storage tier includes several storage devices, usually hard disk drives (HDDs), but can also include SSDs, CDs, DVDs, and tape drives. Storage devices in a SAN can be organized into RAID groups to increase storage capacity and improve reliability.
SAN technology supports a variety of protocols that allow layers, applications, and operating systems to communicate. The most commonly used protocol is Fibre Channel Protocol (FCP) based on Fibre Channel (FC) technology. The Internet Small Computing System Interface (iSCSI) is a less expensive alternative to FC, often used by small and medium-sized organizations.
- What Is A Storage Area Network Used For
- SANs are often used to consolidate storage. For example, computer systems (eg, servers) typically include one or more local storage devices. But consider a data center with hundreds of servers, each running virtual machines that can be deployed and migrated between servers as needed. If a workload's data is stored on this local storage, it may also be necessary to move the data when migrating the workload to another server, or to restore the data in the event of a server failure. Rather than trying to organize, track, and use physical disks located in individual servers throughout the data center, businesses may choose to move storage to dedicated storage subsystems, such as storage arrays, where storage can be centrally provisioned, managed, and managed. protected.
- SANs can also improve storage availability. Because a SAN is essentially a network fabric that interconnects computers and storage devices, interruptions in one network path can often be overcome by enabling alternate paths through the SAN fabric. Therefore, a single cable or device failure will not render enterprise workloads inaccessible to storage. Additionally, the ability to treat storage as a collective resource can improve storage utilization by eliminating "forgotten" disks on underutilized servers. Instead, a SAN provides a central location for all storage and enables administrators to centralize and manage storage devices.
[More to come ...]
