This chapter is from the book
This chapter is from the book
This chapter is from the book
Storage Devices
High-performance and reliable storage infrastructure forms the basis of storage networks. SANs support a rich variety of storage devices that you can use to store large amounts of data and ensure the high-speed retrieval of data. The most commonly implemented Fibre Channel storage devices are the following:
- Disk arrays
- JBODs
- Tape libraries and subsystems
- Storage servers
The following sections describe each of these devices.
Disk Arrays
A disk array, also referred to as a Redundant Array of Inexpensive Disks (RAID) disk array, is a set of high-performance, high-speed storage disks that can store up to several terabytes of data. The main features of disk arrays include the following:
High-speed data transfers—Disk arrays do not store data serially. Rather, large blocks of data are stored in parallel on several storage disks. When a large amount of data is accessed from or stored on the disk array, high transfer speeds are achieved by accessing or storing data from or to multiple storage disks in parallel.
High reliability—Disk arrays offer high reliability. Even if a large number of components of the disk array fail, the overall device continues to function. Moreover, disk arrays support multiple paths to the network. As a result, problems related to a single point of failure are avoided successfully by the implementation of disk arrays.
NOTE
For detailed information on RAID technology, see Appendix A, "RAID Technology and Fibre Channel Vendors."
Disk arrays are costly Fibre Channel devices. The cost of a typical disk array ranges from $18,000 to $50,000 and up. HP, IBM, Adaptec, Veritas, and Sun Microsystems are some of the vendors of disk arrays.
JBOD
A JBOD is a set of multiple storage disks that you implement as one single logical volume. Data is stored redundantly on multiple disks. The use of multiple disks as one volume is referred to as spanning. However, the vernacular and more famous term associated with spanning in the field of storage devices is JBODs.
Unlike disk arrays, JBODs are not configured for RAID levels. As a result, they do not offer fault tolerance. Although treated as a single logical entity, JBODs do not offer high-performance in terms of access speed when compared to the independent use of constituent disks.
The price of JBODs ranges from $500 to $2000. HP, Hitachi, Compaq, Dell, Network Storage Solutions, and IBM are some of the JBOD vendors.
Tape Libraries and Subsystems
Tape storage is one of the most cost-effective and reliable backup technologies. It offers a huge storage capacity that ranges from 10 GBs to 1000 TBs. A tape library consists of a set of tape cartridges that are used to store data. In addition to the tape cartridges, a tape library also consists of a tape subsystem that includes the hardware interface to facilitate commun-ication between the host processor and the library.
In addition to the large amount of data space that tape libraries offer, the tape cartridges are capable of mounting and dismounting automatically. This makes them highly manageable and administrator-independent.
IBM, HP, Compaq, Quantum Corp., and Compaq are some of the most well-known vendors of tape storage. Despite the huge storage space they offer, the prices of tape storage are low as compared to other storage devices. The price of tape storage ranges from $2500 to $10,000.
Storage Servers
Storage servers are the focal point of any storage infrastructure that can support a wide range of clients. These servers are high-performance, highly reliable, and scalable storage devices that can store up to several terabytes of data. You can integrate additional storage servers into the existing storage network without the need of costly upgrades.
The price of storage servers ranges from $2000 to $10,000 and up. IBM, HP, Compaq, and Cisco are some well-known storage server vendors.