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BP1028 EqualLogic iSCSI for Fibre Channel Professionals 9
An FC system may have a mix of drive types (such as FC, SAS, SATA, and SSD disk), or it may only have
a single type. Depending on the type of array, it may have multiple ports for front-end and back-end
connectivity. Some may even support additional connectivity options (such as SAS, iSCSI, etc.) or NAS
features (for support of NFS and CIFS protocols over Ethernet). Typical systems are built around
redundant hardware components throughout and cache memory that is protected against power loss.
Many FC storage systems traditionally require the administrator to make choices about disk
configuration and placement. For example, a group of disks may be configured as part of a RAID set, a
RAID policy assigned to the set of disks, and then logical volumes are created and assigned to hosts.
Mapping of a volume is usually made as a logical unit (or LUN) that is presented by the controller units
or targets.
6.2 EqualLogic PS Series arrays
An EqualLogic PS Series array uses the iSCSI protocol over standard Ethernet switching. While it is
technically possible to deploy an EqualLogic storage solution on an existing Local Area Network (LAN),
it is recommended to isolate iSCSI storage traffic to a dedicated storage network. Creating a dedicated
iSCSI SAN network, with its own dedicated bandwidth, allows for more deterministic performance
similar to that of a dedicated FC SAN.
Like most FC storage systems, EqualLogic PS Series arrays also contain redundant power and
controllers, and protected cache memory. However, one of the key differences in the EqualLogic
architecture is its ability to scale both capacity and performance as additional arrays are added. Each
PS Series array contains disk, cache memory, network controller ports, and CPUs so when the storage
system is expanded, adding another array adds more of each of these resources. The “PS” stands for
“Peer Storage”, which is a reference to how the members communicate with one another.
As arrays are added to the group, data is automatically spread across multiple members of the storage
group. A typical volume may extend across 1-3 members in a PS Series group. Mapping of volumes is
virtualized, and each volume is presented to the host as a separate target with a single LUN (LUN0)
that is the volume.
Figure 4 - EqualLogic scale-out architecture