D-Link DSN-656 User Manual - Page 151

Glossary and Acronym List

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D-Link Document - User Manual Glossary and Acronym List Common Terminology Item RAID PD RG VD LUN GUI RAID cell WT WB RO DS LS GS Description Redundant Array of Independent Disks. There are different RAID levels with different degree of data protection, data availability, and performance to host environment. The Physical Disk belongs to the member disk of one specific RAID group. Raid Group. A collection of removable media. One RAID group consists of a set of virtual disks and owns one RAID level attribute. Virtual Disk. Each RAID group could be divided into several virtual disks. The virtual disks from one RAID group have the same RAID level, but may have different volume capacity. Logical Unit Number. A logical unit number (LUN) is a unique identifier which enables it to differentiate among separate devices (each one is a logical unit). Graphic User Interface. When creating a RAID group with a compound RAID level, such as 10, 30, 50 and 60, this field indicates the number of subgroups in the RAID group. For example, 8 disks can be grouped into a RAID group of RAID 10 with 2 cells, 4 cells. In the 2-cell case, PD {0, 1, 2, 3} forms one RAID 1 subgroup and PD {4, 5, 6, 7} forms another RAID 1 subgroup. In the 4- cells, the 4 subgroups are physical disk {0, 1}, physical disk {2, 3}, physical disk {4, 5} and physical disk {6,7}. Write-Through cache-write policy. A caching technique in which the completion of a write request is not signaled until data is safely stored in non-volatile media. Each data is synchronized in both data cache and accessed physical disks. Write-Back cache-write policy. A caching technique in which the completion of a write request is signaled as soon as the data is in cache and actual writing to non-volatile media occurs at a later time. It speeds up system write performance but needs to bear the risk where data may be inconsistent between data cache and the physical disks in one short time interval. Set the volume to be Read-Only. Dedicated Spare disks. The spare disks are only used by one specific RAID group. Others could not use these dedicated spare disks for any rebuilding purpose. Local Spare disks. The spare disks are only used by the RAID groups of the local enclosure. Other enclosure could not use these local spare disks for any rebuilding purpose. Global Spare disks. It is shared for rebuilding purpose. If some RAID groups need to use the global spare disks for rebuilding, they could get the spare disks out from the common spare disks pool for such requirement. Copyright@2014 D-Link System, Inc. All Rights Reserved. 151

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D-Link Document – User Manual
Glossary and Acronym List
Common Terminology
Item
Description
RAID
Redundant Array of Independent Disks. There are different RAID levels
with different degree of data protection, data availability, and
performance to host environment.
PD
The Physical Disk belongs to the member disk of one specific RAID group.
RG
Raid Group. A collection of removable media. One RAID group consists of
a set of virtual disks and owns one RAID level attribute.
VD
Virtual Disk. Each RAID group could be divided into several virtual disks.
The virtual disks from one RAID group have the same RAID level, but may
have different volume capacity.
LUN
Logical Unit Number. A logical unit number (LUN) is a unique identifier
which enables it to differentiate among separate devices (each one is a
logical unit).
GUI
Graphic User Interface.
RAID cell
When creating a RAID group with a compound RAID level, such as 10, 30,
50 and 60, this field indicates the number of subgroups in the RAID
group. For example, 8 disks can be grouped into a RAID group of RAID 10
with 2 cells, 4 cells. In the 2-cell case, PD {0, 1, 2, 3} forms one RAID 1
subgroup and PD {4, 5, 6, 7} forms another RAID 1 subgroup. In the 4-
cells, the 4 subgroups are physical disk {0, 1}, physical disk {2, 3}, physical
disk {4, 5} and physical disk {6,7}.
WT
Write-Through cache-write policy. A caching technique in which the
completion of a write request is not signaled until data is safely stored in
non-volatile media. Each data is synchronized in both data cache and
accessed physical disks.
WB
Write-Back cache-write policy. A caching technique in which the
completion of a write request is signaled as soon as the data is in cache
and actual writing to non-volatile media occurs at a later time. It speeds
up system write performance but needs to bear the risk where data may
be inconsistent between data cache and the physical disks in one short
time interval.
RO
Set the volume to be Read-Only.
DS
Dedicated Spare disks. The spare disks are only used by one specific RAID
group. Others could not use these dedicated spare disks for any
rebuilding purpose.
LS
Local Spare disks. The spare disks are only used by the RAID groups of the
local enclosure. Other enclosure could not use these local spare disks for
any rebuilding purpose.
GS
Global Spare disks. It is shared for rebuilding purpose. If some RAID
groups need to use the global spare disks for rebuilding, they could get
the spare disks out from the common spare disks pool for such
requirement.
151
Copyright@2014 D-Link System, Inc. All Rights Reserved.