Specifications
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Technology Overview
Xserve RAID
Expanding arrays
Adding more disks to an existing array is accomplished using RAID Admin. Expanding
an array preserves the existing array while making available the capacity of the added
drives. Expansion in RAID Admin restripes the data across the entire set of new disks
to provide optimal performance and capacity utilization.
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Slicing arrays
To share a single RAID set across multiple servers, RAID Admin allows you to divide
it into smaller segments, or “slices.” Each slice becomes a separate LUN, or logical unit
number, so the host system can manage it as a discrete volume. Instead of creating
many small arrays for individual servers, this “pooling and distributing” technique
enables administrators to leverage the storage efficiencies of a large consolidated
array. RAID Admin can slice up to 6 LUNs per RAID controller and produce up to
16 LUNs per Xserve RAID system.
Enhanced JBOD mode
Enhanced JBOD mode allows each drive to become a separate LUN. This mode is
especially useful for high-end database applications that have specic needs on
how data is addressed. These applications provide protection using specialized host
mirroring and striping. Xserve RAID provides JBOD performance that is enhanced by
using the RAID controller’s sophisticated adaptive Write Cache and Read Pre-fetch.
When using enhanced JBOD mode, hardware slicing is disabled; therefore, this mode
is recommended only for applications that provide these features.
Steady Streaming mode
Steady Streaming mode allows Xserve RAID users to provide consistent read latency
for applications requiring it. Steady Streaming mode can compensate for the mechani-
cal instabilities and external vibrations that can cause a hard drive to deliver data to
the system with undesirable latency.
Background scan and repair
Xserve RAID enables remote background scans to repair or map out bad blocks on a
RAID set. You can set a load-sharing priority, allowing the background scan to operate
without causing a signicant degradation in overall RAID set performance.
Advanced capabilities are easy enough for a
novice and powerful enough for an expert.