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EMCFib re Channel Storage Systems ConfigurationPlanning Guid e
Storage System Hardware
Hardware for Unshared Storage
Unshared storage systems are less costly and less complex than
shared storage systems. They offer many shared storage system
features; for example, you can use multiple unshared storage systems
with multiple servers. However, with multiple servers, unshared
storage offers less flexibility and security than shared storage, since
any user with write access to privileged server files can enable access
to any storage system.

Types of Storage System for Unshared Storage

For unshared storage, there are four types of storage system, each
using the FC-AL protocol. Each type is available in a rackmount or
deskside (office) version.
•Disk-array Processor Enclosure (DPE) storage systems. A DPE is
a 10-slot enclosure with hardware RAID features provided by one
or two storage processors (SPs). In addition to its own disks, a
DPE can support up to 110 additional disks in 10-slot Disk Array
Enclosures (DAEs) for a total of 120 disks. This is the same kind of
storage system used for shared storage, but it uses a different
storage processor (SP).
•Intelligent Disk Array Enclosure (iDAE). An iDAE, like a DPE,
has SPs and thus all the features of a DPE, but is thinner and has a
limit of 30 disks.
•Disk Array Enclosure (DAE). A DAE does not have SPs. A DAE
can connect to a DPE or an iDAE, or you can use it without SPs. A
DAE used without an SP does not inherently include RAID, but
can operate as a RAID device using software running on the
server system. Such a DAE is also known as Just a Box of Disks, or
JBOD.