hot spare or hot | A drive in a RAID 1 or RAID 5 configuration that is held in reserve to replace any other | ||
sparing | drive that fails. After a reconstruction, the | ||
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The ability to remove, replace or add a device while power is still applied but all I/O | |||
| processes are suspended. |
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The ability of a | |||
| remains powered on and operational. | ||
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ID | Identifier number |
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IEC | International Electrotechnical Commission | ||
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initialization | The process of writing a specific pattern to all data blocks on all drives in a logical drive. | ||
| This process overwrites and destroys existing data on the disks and the logical drive. | ||
| Initialization is required to make the entire logical drive consistent at the onset. | ||
| Initialization ensures that any parity checks performed in the future will execute correctly. | ||
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IOPS | Input/output operations per second. A measure of I/O performance, this is usually used to | ||
| quote random I/O performance. See throughput. | ||
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JBOD | Just a Bunch Of Disks. JBOD refers to a group of drives without an embedded RAID | ||
| controller; generally, such a group is used without RAID formatting, with a | ||
| hardware RAID controller, or with RAID formatting from host software (with no | ||
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LAN | Local Area Network |
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LD | Logical drive |
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logical drive | A section of disk storage space, also referred to as a LUN, that is presented to the host | ||
| operating environment as a single physical drive. A logical drive may be located on one or | ||
| more physical drives. Each array controller can manage one to eight logical drives | ||
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LUN | Logical unit number. A LUN is a set of physical drives in a RAID configuration that are | ||
| seen by the operating system as one virtual drive. | ||
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LUN mapping | The ability to change the virtual LUN as presented to the server from storage. This enables | ||
| such benefits as the ability of a server to boot from the SAN without requiring of a local | ||
| disk drive. Each server requires LUN 0 to boot. | ||
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LUN masking | The characteristic that enables an administrator to dynamically map an HBA to a specified | ||
| LUN. This provides an individual server or multiple servers access to an individual drive | ||
| or to multiple drives, and prohibits unwanted server access to the same drives. | ||
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LVD | A | ||
| communication between a supported server and storage devices. LVD signaling uses two | ||
| wires to drive one signal over copper wire and requires a cable that is no longer than 25 | ||
| meters (82 ft.). |
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MB | Megabyte. 1,000,000 bytes or characters of data. | ||
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mirroring: RAID 1 | Data written to one disk drive is simultaneously written to another disk drive. If one disk | ||
| fails, the other disk can be used to run the array and reconstruct the failed disk. The | ||
| primary advantage of disk mirroring is 100% data redundancy. Since the disk is mirrored, | ||
| it does not matter if one of the disks fails. Both disks contain the same data at all times and | ||
| either can act as the operational disk. Disk mirroring provides 100% redundancy, but is | ||
| expensive because each drive in the array is duplicated. | ||
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MTBDL | Mean time between data loss. In a RAID system, this is the average expected time | ||
| between two rapid disk failures that would cause irreparable data loss. | ||
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MTBF | Mean time between failures. A measure of reliability, this is the average expected time | ||
| between failures of equipment, usually measured in operating hours. | ||
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MTTR | Mean time to repair. A measure of availability, this is the average time the system is out of | ||
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