HP NetRAID 1Si Controller - Manual (Page 149)

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Glossary
HP NetRAID Terms and Technology
Array: An array of disk modules combines the storage space on the disk modules
into a single segment of contiguous storage space. HP NetRAID can group disk
modules on one or more of its SCSI channels into an array. A hot spare disk
module does not participate in an array.
Array Spanning: Array spanning by a logical drive combines storage space of
two, three, or four arrays of disk modules into a logical drive’s single, contiguous
storage space.
Logical drives can span consecutively numbered arrays that each consist of the
same number of disk modules. Array spanning promotes RAID levels 1, 3, and 5
to RAID levels 10, 30, and 50, respectively.
BIOS: (Basic Input/Output System) The part of the operating system of the
computer that provides the lowest level interface to peripheral devices.
Cache Policy: HP NetRAID lets you choose one of two cache policies:
•
Cached I/O: Reads are always cached regardless of randomness, and the
selected Read policy (Read Ahead, Normal, or Adaptive) and Write policy
(Write-Through and Write-Back) applies.
•
Direct I/O: First reads to a new location always come directly from the
disk. If a location is read repeatedly, then the Read policy (Read Ahead,
Normal, or Adaptive) as selected applies and the read data is cached. Read
data is cached only if accessed repeatedly. With 100% random reads,
nothing is cached.
Capacity Expansion (or Volume Expansion): Allows you to increase the size of
an existing volume while remaining online under Microsoft Windows NT or
Windows 2000 or under Novell NetWare 4.2 or 5.
•
Under Microsoft Windows 2000 or NetWare or 5, leave virtual sizing
disabled to prepare for online capacity expansion.
•
Under Windows NT or NetWare 4.2, enable virtual sizing to prepare for
capacity expansion. The controller creates virtual space when the Virtual
Sizing option is enabled in the HP NetRAID Express Tools utility. A
volume can then be expanded into the virtual space by adding a physical
disk through reconstruction.