by September 19, 2001 0 comments

Various components are used to build a SAN (Storage Area Networks), the major ones being hubs, switches, bridges, RAID storage devices, backup devices, servers, and cabling. Most of these components are fairly known in networking. We will take a look at their significance in a SAN.

Fiber channel: A SAN’s lifeline

Fiber has always been used in networks needing high-speed data transfers, and things are no different when comes to SAN also. Since a SAN involves backing up huge volumes of data, a high-speed interface like an FC (Fiber Channel), which can support data transfers as high as 4 GB/sec is a must. It is a high-performance serial I/O interface, which is media independent and supports simultaneous transfers of different protocols. It can be placed over longer distances than most other high-speed interface options such as SCSI and Ethernet. Your SAN solution provider usually provides the cabling along with the other infrastructure.

SAN storage system

Since a SAN solution deals with high volumes of data, it requires a highly reliable storage solution like a RAID system. RAID (Redundant Array of Inexpensive Disks), as the name suggests, creates data redundancy for data protection and fault tolerance. The storage capacity of RAID systems ranges from 500 GB to a few 100 TB (terabytes), making them highly scalable. A RAID system basically combines multiple smaller drives into arrays, and presents them as one single LUN (Logical Storage Unit LUN). The drive arrays make use of various techniques to make the data fault-tolerant. These are referred to as RAID levels, ranging from 0 to 5 and differ in the way they provide data redundancy and I/O performance. Many SAN solution providers use their own techniques to enhance their RAID systems, including redundant cooling systems and power supplies; and monitoring features. Key players in RAID solutions for SANs include Dell, HP, IBM, Compaq, and Sun Microsystems.

Tivoli from IBM offers a complete management solution

Dell’s PowerVault 660F is a fiber-channel RAID array that provides 500 GB of storage space in a 3U rack mounted chassis.

You can increase storage capacity up to 7 TB by adding PowerVault 224F expansion enclosures.

A high-end disk storage array from HP called HP Surestore disk array xp512, offers support for RAID level 0/1 and level 5 for storage performance. It also offers the choice of 18 GB, 15,000 rpm; and 73 GB, 10,000 rpm fiber-channel drives. It is scalable up to 512 disks, 37 TB of storage, and can support 32 host connections. The array is also battery protected to make sure your data is safe in case of power problems.

SAN solutions use a fiber-channel interface as it can give  high transfer speeds to the order of 4GB/secBesides RAID, tape drives can also be used as backup devices for a SAN. These have an FC interface for faster I/O performance. You can also use your legacy SCSI backup devices by using an FC bridge.

SAN backup devices have the advantage that you don’t need a dedicated server for doing backups as in the case of traditional backup devices. In a SAN environment, the server only directs the data to be backed up to a drive. The data is then directly moved from disk-to-disk or disk-to-tape without any further intervention from the server. FC hubs and switches also have some instructions built into them to ensure that the data reaches the appropriate destination. This frees up the server for other productive tasks.

The IBM Magstar 3494 Tape Library can connect up to 32 SCSI or FC drives, with a capacity of up to 748 TB. It can use both IBM 3490 E or Magstar3590 tape drives. It has support for HP, Sun and Widows NT platforms, and allows multiple hosts to share simultaneously.

Interconnectivity devices: Hubs, switches, and bridges

The Sun StorEdge Network FC switch has 16 ports that provide 1 GB/sec at each port. It also comes with a GUI management tool for easy configuration Hubs, switches, and bridges are used to interconnect the various components in a SAN. They are different from their ordinary counterparts in that they are based on FC, and can be placed up to 10 km apart. The HP Surestore L10/S10 hub for example, provides 10 FC ports and 10 km connectivity. These interconnectivity devices can also be used to increase the number of devices on your SAN. Bridges let you connect different types of interfaces together. For example, an FC to SCSI bridge will let you use your legacy SCSI devices, while still using FC technology. The HP SureStore SCSI bridge fc 2/1 lv for instance, has one fiber port to two LVD SCSI ports and includes all the accessories needed to connect fiber with up to two SCSI HP Ultrium drives in the HP Surestore tape libraries.

SAN software

HP’s SureStore backs up Windows clients on your network and does disaster recovery tooSoftware in a SAN environment is as important as the hardware that goes into it. Most software solutions let you carry out tasks such as volume management, server-less backups, and configuration of different SAN components. Vendors have their own proprietary SAN software, which has been custom designed for their specific range of products. There are also companies like Legato Systems and Veritas Software who specialize in SAN software that works with hardware from most vendors.

IBM has various categories of SAN software for management, protection, and file sharing. For instance, its Tivoli Storage Network Manager offers a complete SAN management solution that discovers, displays, allocates, monitors, automates and manages SAN components and disk storage devices.


Links to SAN Solutions
SAN Fiber Channel

SAN solutions from various vendors
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SAN software

Legato Systems:

Legato is one of the leading SAN software solution developers, which many hardware providers support. Their range of software products has been divided into three broad segments: Protection, Availability, and Data management. For data protection, you can use their Celestra Power to free network and server resources from backup and restore operations through live server-less LAN-free backups. The latest release provides support for 64-bit Solaris and HPUX platforms. It also offers a Celestra Module for Oracle (CMO), which allows you to take server-less backups of TB-sized Oracle databases.


Veritas’ SAN line of products is called Veritas SANpoint, and is a comprehensive set of SAN management tools, comprising SANPoint control, SANPoint Direct, and SANPoint Foundation Suite HA.

Veritas SANPoint Control is an enterprise-level management tool for automatically locating, viewing, and administering SAN-connecting devices from a central console. Veritas SANPoint Direct is for sharing data in Windows 2000/NT environments. And finally, Veritas SANPoint Foundation Suite HA provides data sharing in a typical SAN based environment.

Since SAN is still an emerging technology, standards have not yet fully evolved. So SAN components purchased from different vendors may not work together, leading to interoperability headaches. Currently therefore, various SAN solution providers are coming out with their own complete SAN solutions, or SAN in a box. This is a set of pre-configured SAN components that can easily be deployed in any environment. Such a solution removes the hassles involved in connecting devices from multiple vendors.

Sachin Makhija

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