Dell PERC 4/SI - Manual (Page 71)

Hot Swap Disk Drive
Hot swap drives allow a system administrator to replace a failed disk drive in a system without powering down the system and suspending services. The hot
swap drive is pulled from its slot in the drive cage; all power and cabling connections are integrated into the drive enclosure backplane. The replacement hot
swap drive can then slide into the slot. Hot swapping only works for RAID 1, 5, and 10 configurations.
Initialization
The process of writing zeros to the data fields of a logical drive and, in fault tolerant RAID levels, generating the corresponding parity to put the logical drive in
a Ready state. Initializing erases previous data and generates parity so that the logical drive will pass a consistency check. Arrays will work without initializing,
but they can fail a consistency check because the parity fields have not been generated.
I/O Driver
A host system software component (usually part of the operating system) that controls the operation of peripheral adapters attached to the host system. I/O
drivers communicate between applications and I/O devices and in some cases participate in data transfers.
Logical Drive
A complete or partial representation of a logical array. The storage space in a logical drive is spread across all the physical drives in the array or spanned
arrays. Each RAID controller can be configured with up to forty logical drives in any combination of sizes. Configure at least one logical drive for each array. A
logical drive can be in one of three states:
l Online: All participating disk drives are online.
l Degraded: (Also "Critical") a single drive in a redundant array (not RAID 0) is not online. Data loss can occur if a second disk drive fails.
l Offline: Two or more drives in a redundant array (not RAID 0) or one or more drives in a RAID 0 array are not online.
I/O operations can be performed only with logical drives that are online or degraded.
Mapping
The relation between multiple data addressing schemes, especially conversions between member disk block addresses and block addresses of the virtual
disks presented to the operating environment by array management software.
MB
A megabyte; an abbreviation for 1,000,000 (10 to the sixth power) bytes.
Mirroring
The process of providing complete redundancy using two disk drives, by maintaining an exact copy of one disk drive's data on the second disk drive. If one disk
drive fails, the contents of the other disk drive can be used to maintain the integrity of the system and to reconstruct the failed drives.
Multi-threaded
Having multiple concurrent or pseudo-concurrent execution sequences. Multi-threaded processes allow throughput-intensive applications to efficiently use
resources to increase I/O performance.
Ns
A nanosecond, 10^-9 second.
Online
An online device is a device that is accessible.
Online Expansion
Capacity expansion by adding volume or another hard drive, while the host system is accessible and/or active.
Operating Environment
An operating environment can include the host system where an array is attached, any I/O buses and adapters, the host operating system and any additional
software required to operate the array. For host-based arrays, the operating environment includes I/O driver software for the member disks but does not
include array management software, which is regarded as part of the array itself.
Parity
An extra bit added to a byte or word to reveal errors in storage (in RAM or disk) or transmission. Parity is used to generate a set of redundancy data from two
or more parent data sets. The redundancy data can be used to reconstruct one of the parent data sets. However, parity data does not fully duplicate the
parent data sets. In RAID, this method is applied to entire drives or stripes across all disk drives in an array. Parity consists of dedicated parity, in which the
parity of the data on two or more drives is stored on an additional drive, and distributed parity, in which the parity data are distributed among all the drives in
the system. If a single drive fails, it can be rebuilt from the parity of the applicable data on the remaining drives.
Partition
A complete or partial representation of a logical drive, usually represented to a user by an operating system as a physical disk. Also called a logical volume.
PERC 4e/Di
The DellTM PERC 4e/Di consists of an LSI 1030 chip on the motherboard to offer RAID control capabilities. PERC 4e/Di supports all dual-ended and LVD SCSI
devices on Ultra320 and Wide SCSI channels with data transfer rates up to 320 MB/s (Megabytes per second).