An informational and technical guide to selecting the best hard drive for building a new computer or upgrading a current system.



How to Choose the Right
Hard Drive

IDE vs. SCSI Hard Drives


IDE/ATA
Hard Drives

SCSI
Hard Drives

External
Hard Drives

Fibre Channel Hard Drives

Firewire
IEEE 1394
Hard Drives

USB and Portable
Hard Drives

RAID
Hard Drives

Formatting a Hard Drive

Glossary of Hard Drive Terms

 

    

Fibre Channel Hard Drives

    Fibre Channel is a high performance computer hard drive interface designed to bring speed and flexibility to multiple disc drive storage systems. The intention of the Fibre Channel (FC) is to develop practical, inexpensive, yet expendable means of quickly transferring data between workstations, mainframes, supercomputers, desktop computers, storage devices, displays and other peripherals. Fibre Channel is the general name of an integrated set of standards being developed by the American National Standards Institute (ANSI)

Key Features of Fibre Channel Hard Drives

  • Hot-plugging capability – Fibre Channel hard drives can be installed or removed while the host system is operational. This can be crucial in high-end and heavy-use server systems where there is little or no downtime.
  • ANSI standard compliance for serial port interface – Fibre Channel hard drives do not require special expensive adapters.
  • Speed – In its intended environment, Fibre Channel is the fastest option available.
  • Cost effectiveness – Compard to other high-end solutions, Fibre Channel is inexpensive because it does not require special adapters.
  • Loop resiliency – Fibre channel provides high data integrity in multiple-drive systems, including Fibre Channel RAID (Redundant Array of Independent (Inexpensive) Disks)
  • Longer cable lengths – Compared to LVD, Fibre Channel can maintain data integrity through significantly longer cables. This makes configuring multiple devices easier.

What is the main use for Fibre Channel Hard Drives?

    Fibre Channel hard drives were designed for use in multiple-drive system environments like servers. A Fibre Channel configuration consists of a backplane, which is an external enclosure that houses a printed circuit board (PCB) and multiple drive receptacles, and a Fibre Channel host bus adapter (HBA). The backplane allows direct connection to the hard drives (no cable), supplies power to the drives, and controls the input and output of data on all drives within the system. Because so much of Fibre Channel's benefits are derived from its method of data handling among multiple drives, single drive environments will realize no significant performance enhancement by using Fibre Channel over LVD.

  SCSI Wide (LVD) Fibre Channel
Higher Bandwidth 40-80 mBytes/sec 100 Mbyts/Sec
More Connectivity 15 Devices 126 Devices
Simplified Attachment Ribbon Cable, Jumpers, Power SCA Backplane: no jumpers, switches or power connections
Increased Distance 1.5 Meters total length (single ended)
12 Meters total length		 30 Meters device to device (copper)
10 Kilometers device to device (optical)
Improved redundancy Parity and running disparity CRC protected frames
Simplified interface Wide, Narrow, SCA, Fast, Ultra, Single-Ended, LVD, HVD 1 version only

Dual Loops. What are they?

     Dual loops allow Fibre Channel hard drives to be connected to two separate server environments at the same time.  While only one loop can access the drive at any given moment, dual loops allow both servers to share the drive without manually switching.

How dual loops improve performance.

      Most often, dual loops improve performance by sharing data. This means data used by more than one system can be stored in a central location and accessed by both loop systems. This eliminates the need to duplicate or synchronize data.

     If duplicate synchronous data is not the issue, Fibre Channel hard drives can connect to two independent loops at the same time. Each loop can transfer data at up to 100 Mbytes/second. While theoretically that means a dual loop system can transfer data at up to 200 Mbytes/sec, in a traditional Fibre Channel system, the controller can access only one loop at a time, which means the maximum data transfer rate is about 100 Mbytes/second.  In a Fibre Channel RAID system, however, the maximum transfer rate can increase significantly depending on the number of drives: the more drives present, the faster the data transfer rate.

How many drives can be connected to a single Fibre Channel hard drive loop?

     Fibre Channel drives use an SCA (Single Connector Attachment) connection that combines the data signals and power supply lines into a single connection. This makes it possible for a maximum of 126 Fibre Channel drives to connect to a single loop at the same time.

How many drives can be connected to a Fibre Channel hard drive dual loop system?

     In a dual loop system, it is possible to have 126 drives connected to each loop, for a maximum of 252 drives. It is important to note that any shared drives will detract from the total number. There can only be 252 total if there are 0 shared drives.

What is the maximum cable length recommended between Fibre Channel hard drives?

     The maximum cable length recommended between Fibre Channel devices is 30 meters using copper and 10 kilometers (6 miles) using fiber optics. This is significantly longer than LVD's maximum cable length of 12 meters. It is important to note that exceeding recommended maximum cable length can significantly impact data integrity.

 

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