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ACCESS – |
|
Read, write, or update information on a storage medium. |
| AVAILABILITY
– |
| The amount of time
that a system is available during those time periods when it
is expected to be available. Availability is often measured
as a percentage of an elapsed year. For example, 99.95% availability
equates to 4.38 hours of downtime in a year (0.0005 * 365 *
24=4.38) for a system that is expected to be available all the
time. |
| AVERAGE
LATENCY - |
- Average Response Time (ms) - Average time between initiation
and completion of an I/O operation in milliseconds.
- Average Read Response Time (ms) - Average time between
initiation and completion of a read operation.
- Average Write Response Time (ms) - Average time between
initiation and completion of a write operation.
- Average Transaction Time (ms) - Average time between
initiation of a request and completion of the corresponding
reply.
|
| AVERAGE
SEEK TIME - |
| The average time
it takes for the read/write head to move to a specific location.
To compute the average seek time, divide the time it takes to
complete a large number of random seeks by the number of seeks
performed. |
 |
 |
| BANDWIDTH
- |
| Bandwidth is the
total amount of data that can be transferred at one time between
CPU and storage. Generally, bandwidth refers to large block
data transfers and is usually measured in MB/sec. (For instance,
the total bandwidth available on any given Ultra SCSI bus is
40 MB/sec.) Actual transfer rates are somewhat less than this.
|
| BACKUP
- |
(noun) A collection
of data stored on (usually removable) non-volatile storage
media for purposes of recovery in case the original copy of
data is lost or becomes inaccessible. Also called backup copy.
To be useful for recovery, a backup must be made by copying
the source data image when it is in a consistent state.
(verb) The act of creating a backup. |
| BACKUP
WINDOW - |
| The period of time
available for performing a backup. Backup windows are typically
defined by operational necessity. For example, if data is used
from 8AM until midnight, then the window between midnight and
8AM is available for making backup copies. For consistent backups,
data may not be altered while the backup is occurring, so in
some cases a backup window is an interval of time during which
data and applications are unavailable. |
| BLOCK
- |
| A sector or group
of sectors. By default, a sector of data consists of 512 bytes. |
| BYTE
- |
| Shortened form of
binary table, a byte is a group of eight bits handled as a logical
unit. |
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|
| CACHE
- |
| Same technology
as cache memory used in servers. Storage cache usually resides
on RAID controllers and boosts performance because the CPU doesn't
have to wait for a disk head to spin. Data can be written to
and read directly from cache. |
| CONTROL
SOFTWARE - |
| A body of software
that provides common control and management for one or more
disk arrays or tape arrays. Control software presents the arrays
of disks or tapes it controls to its operating environment as
one or more virtual disks or tapes. |
| CPU
– |
| Central Processing
Unit. |
| CPU
Effectiveness - |
| Total I/Os per second
divided by % CPU Utilization, giving a measure in I/Os per second
per CPU. Indicates how efficient the I/O subsystem is in CPU
utilization. |
| CPU
Utilization (total) - |
| Percentage of processor
time spent executing threads other than the Idle thread (in
other words, time spent doing useful work). Also know as % Processor
Time. |
|
|
| Dedicated
Hot Spare - |
| The hot spare drive
which is configured to replace failed hard drive only for designated
RAID within the storage device. |
| DPC
Time - |
| Percentage of processor
time spent in Deferred Procedure Calls. |
| DISASTER
RECOVERY - |
| Preventative measures
including fault tolerant systems, redundant hardware, and specialized
software to ensure that businesses can operate during certain
failures, and quickly recover data, hardware and communications
assets. |
| DISK
- |
| Any storage unit
presented as a single contiguous block of storage. From a hardware
perspective, a disk can be a physical local drive, external
SCSI attached storage, or a LUN created by a RAID controller.
|
| DISK
DRIVES - |
A storage device
attached to a computer or storage device that reads from,
writes to, and stores information on a disk or hard drive.
|
| DISTRIBUTED
STORAGE - |
| Distributed storage
is set up so that each server has its own external storage subsystem.
|
| Dynamic
Disks - |
| Contain volume manage
management databases comprising information on all other dynamic
disks and volumes on a system. |
|
|
| FAILOVER
- |
| The automatic substitution
of a functionally equivalent system component for a failed one.
The term failover is most often applied to intelligent controllers
connected to the same storage devices and host computers. If
one of the controllers fails, failover occurs, and the survivor
takes over its I/O load. |
| FILE
MANAGEMENT - |
| The ability to manage
the file level data that resides on your storage. This encompasses
direct file monitoring and the monitor and control of the space
being utilized. An aspect of Storage Resource Management. |
|
|
| GIGABYTE
(GB) - |
| A unit of measure
consisting of one billion bytes (one thousand megabytes). |
| Global
Hot Spare - |
| The hot spare drive
which is configured to replace failed hard drive for any given
RAID within the storage device. |
|
|
| HOT
SWAPPING - |
| The removal or addition
of components while the system is running. For example, hard
drives, power supplies, PCI cards and buses are often candidates
for this term. |
|
Hybrid Hard Drive - |
Hybrid drive is the next
generation hard drive that combines traditional rotating magnetic
hard drive with large flash memory.
|
|
|
| Interrupt
Time - |
| Percentage of processor
time spent handling hardware interrupts. |
| Interrupts
per Second - |
| Average number of
interrupts per second, averaged over the length of the test
so far. If there are multiple processors, this is the total
number of interrupts for all processors. |
| I/O
- |
| Refers to data that
is being sent from the CPU to any type of storage device or
peripheral. |
| I/O
Size - |
| The transfer request
size that specifies the number of bytes read or written in each
I/O request. You can select any value from 1 byte to almost
1 Gigabyte (limited only by the amount of virtual memory available).
|
| I/O
Type - |
| Specifies the percentage
of read and write operations performed in each operation. You
can have 100% Read, 0% Write, or vice versa or a combination
of both. |
| IOPS
– |
Input/Output operations per
second.
Total IOPS - Average number
of Input/Output operations per second.
Read IOPS - Average number of
read operations per second.
Write IOPS - Average number
of write operations per second.
|
|
iSCSI – |
Encapsulation of SCSI commands
and data over TCP/IP.
|
|
iSCSI – Target |
A storage device which the
iSCSI volumes are created on.
With iSCSI initiator utility and protocol, host server/PC
is able to link to the iSCSI target and use the iSCSI volume
as local hard disk.
|
|
|
| JBOD
- |
| JBOD (for "just
a bunch of disks," or sometimes "just a bunch of drives")
the official term is "spanning" - used to refer to
a computer's hard disks that haven't been configured according
to the RAID (for "redundant array of independent disks")
system to increase fault tolerance and improve data access performance.
The RAID system stores the same data redundantly on multiple
disks that nevertheless appear to the operating system as a
single disk. Although, JBOD also makes the disks appear to be
a single one, it accomplishes that by combining the drives into
one larger logical one. JBOD doesn't deliver any advantages
over using separate disks independently and doesn't provide
any of the fault tolerance or performance benefits of RAID.
|
|
|
| Privileged
Time – |
| Percentage of processor
time spent in Privileged Mode (including the MicrosoftR Windows
NTR service layer, the Executive routines, the Windows NT Kernel,
and device drivers for most devices other than graphics adapters
and printers). |
|
|
| RouStor
– |
| Storage equipment
combined with networking device to provide faster performance,
easy installation, space saving, interoperability, and lower
cost. |
|
|
| Snapshots
- |
| A copy of a set
of files and directories as they were at a particular point
in the past, a read-only copy of the data set frozen at a point
in time. |
| Stack
Master - |
| A storage/server
device that supports capacity expansion function (stackable)
by iSCSI protocol or other means. |
| Stack
Target - |
| A storage device
that is connected to the stack master to expand capacity on
the master device via iSCSI protocol or other means. |
|
|
| User
Time - |
| Percentage of processor
time spent in User Mode (including application and subsystem
code, the graphics engine, graphics device drivers, printer
device drivers, and the window manager). |
|
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|
Wake-on-LAN - |
| Wake-on-LAN is
the ability to switch on the system through special network
packet. The administrator can remotely boot up the system. |
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