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1.3 Terminology The document uses the following terms:
RAID RAID is the abbreviation of “Redundant Array of Independent
Disks”. There are different RAID levels with different degree of the
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 RG consists of a
set of VDs and owns one RAID level attribute.
VD
Virtual Disk. Each RD could be divided into several VDs. The VDs
from one RG have the same RAID level, but may have different
volume capacity.
CV
Cache Volume. Controller uses onboard memory as cache. All RAM
(except for the part which is occupied by the controller) can be used
as cache.
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
width,
RAID
copy,
RAID row
(RAID cell
in one row)
RAID width, copy and row are used to describe one RG.
E.g.:
1. One 4-disk RAID 0 volume: RAID width= 4; RAID copy=1;
RAID row=1.
2. One 3-way mirroring volume: RAID width=1; RAID
copy=3; RAID row=1.
3. One RAID 10 volume over 3 4-disk RAID 1 volume: RAID
width=1; RAID copy=4; RAID row=3.
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.