Dell PowerEdge RAID Controller 5i - Manual (Page 105)

Glossary
103
I
Initialization
The process of writing zeros to the data fields of a
virtual disk and, in fault tolerant RAID levels,
generating the corresponding parity to put the virtual
disk in a Ready state. Initializing erases previous data
and generates parity so that the virtual disk will pass a
consistency check. Virtual disks can work without
initializing, but they can fail a consistency check
because the parity fields have not been generated.
Inter-IC
Inter-IC, also known as I
2
C, is a multi-master bus,
meaning that more than one chip can be connected
to the same bus. Each chip can act as a master and
initiate a data transfer.
M
MB
Acronym for megabyte(s). The term megabyte means
1,048,576 bytes (2^20 bytes); however, when
referring to hard drive storage, the term is often
rounded to mean 1,000,000 bytes.
Mirroring
The process of providing complete redundancy using
two physical disks, by maintaining an exact copy of
one physical disk’s data on the second physical disk. If
one physical disk fails, the contents of the other
physical disk can be used to maintain the integrity of
the system and to rebuild the failed physical disk.
Multi-bit ECC Errors
ECC errors are errors that occur in the memory, which
can corrupt cached data so that it has to be discarded.
ECC double-bit errors are serious, as they result in
corrupted data and data loss. In case of double-bit
ECC errors, contact Dell Technical Support.
N
Non Read Ahead
Non read ahead is a cache read policy. If you select
Non read ahead in the BIOS Configuration Utility,
the controller does not read sequentially ahead of
requested data and store the additional data in cache
memory, anticipating that the data will be needed
soon. Non read ahead is most effective when
accessing random data.
Non Redundant Virtual Disk
A non-redundant virtual disk is one which does not
have redundant data on physical disks that can be
used to rebuild a failed physical disk. A RAID 0 virtual
disk consists of data striped across the physical disks,
without disk mirroring or parity to provide
redundancy. This provides for high data throughput
but offers no protection in case of a physical disk
failure.
Ns
Acronym for nanosecond(s), one billionth of a second.
NVRAM
Acronym for non-volatile random access memory. A
storage system that does not lose the data stored on it
when power is removed. NVRAM is used to store
configuration data on the RAID controller.
O
Offline
A physical disk is offline when it is part of a virtual
disk but its data is not accessible to the virtual disk.
Online
An online device is a device that is accessible.
Dell_PERC5_UG.book Page 103 Tuesday, February 13, 2007 6:02 PM