Appendix A Glossary - ATTO Technology R30F Installation And Operation Manual

Some common terms used in the storage industry are defined below. More information about Fibre
Channel, SCSI and Storage Area Networks is available through the ATTO Technology website
(www.attotech.com), the Fibre Channel Industry Association (www.fibrechannel.org), the Fibre Channel
Consortium (www.iol.unh.edu/consortiums, click on FC), the SCSI Trade Association (www.scsita.org),
and the Storage Area Networking Industry Association (www.snia.org).
Term Definition
address a specific location in memory
ANSI American National Standards Institute
asynchronous a method of sending data over a bus in which an initiator sends data then waits for an
acknowledgement (ACK) that the data has been received. See synchronous.
ATTO The ATTO ExpressRAID_EXT_x.x (x.x represents the software version) is placed in your extensions
ExpressRAID folder during installation of ATTO ExpressRAID to support removable cartridge drives and, in some
Extension cases, for ATTO ExpressRAID to support devices that use LUNs (Logical Unit Numbers), such as the
ATTO SCSI Expander and some hardware controlled RAID arrays.
BER Bit Error Rate: a measure of transmission accuracy; the ratio of bits received in error to bits sent
bit Smallest unit of data a computer can process: a single binary digit with a value of either 0 or 1
block a sector of a disk which stores a group of bytes that must be read or written together. Most systems
and hard disks use 512 bytes in a block.
burst speed maximum speed data can be transferred
Byte an ordered set of 8 bits
CRC Cyclic Redundancy Check: an error-correcting code which calculates a numeric value for received
and transmitted data. If no error has occurred during transmission, the CRC for both received and
transmitted data should be the same.
destination a value in the frame header of each frame which identifies the port in the node where the frame is
address being sent
TM
ExpressWatch monitors the activity of RAID 1 volumes. If a drive failure occurs in a RAID 1 group, ExpressWatch
detects and reports the failure and prompts you to launch ExpressRAID to repair the volume.
ExpressWatch Build in Background (RAID 1 only) equalizes new RAID 1 volumes in the background.
FC Fibre Channel
firmware Software stored in read-only memory (ROM) or programmable ROM (PROM). Firmware is often
responsible for the behavior of a system when it is first switched on.
frame an indivisible unit for transfer of information in Fibre Channel
frame header the first field in the frame containing the address and other control information about the frame.
full duplex a communication protocol which allows transmission in both directions at the same time
half duplex a communication protocol which allows transmission in both directions, but only one direction at a
time
Heartbeat (For EPCI-FC64 only) The heartbeat signal resolves issues if commands remain outstanding on the
Seagate Barracuda drives when using an ATTO ExpressPCI FC host adapter. Do not use it if the host
adapter is connected to a Vixel Rapport 4000 switch. Turn heartbeat off if you are using a Vixel
Rapport 4000 connected to Seagate Barracuda drives. The performance loss to the Barracudas is
less severe than losing the switch connection to the Vixel Rapport 4000.
i ATTO Technology ExpressRAID for Macintosh

Appendix A Glossary