APC RAID Subsystem SCSI-SATA II - Manual (Page 6)

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exceed the highest industry standards, and the best data solution for
small/medium business users.
1.2 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, performance to host
environment.
PD The Physical Disk belongs to the member disk of one specific
volume group.
VG Volume Group. A collection of removable media. One VG
consists of a set of UDVs and owns one RAID level attribute.
UDV
User Data Volume. Each VG could be divided into several
UDVs. The UDVs from one VG share the same RAID level,
but may have different volume capacity.
CV
Cache Volume. IS16GL uses the on board memory as cache.
All RAM (except for the part which is occupied by the
controller) can be used as cache. User can divide the cache
for one UDV or sharing among all UDVs. Each UDV will be
associated with one CV for data transaction. Each CV could
be assigned different cache memory size.
LUN Logical Unit Number. A logical unit number (LUN) is an
unique identifier used on a iSCSI connection which enables it
to differentiate among separate devices (each of which is a
logical unit).
GUI Graphic User Interface.
Caution
Snapshot/rollback features need 512MB RAM or more. Please
refer to RAM certification list in Appendix A for more detail.