Dell EqualLogic PS4100E, Руководство по настройке

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March 2013 Dell EqualLogic Configuration Guide v14.1 14-126
14 Data Center Bridging (DCB)
The enhancement to the Ethernet Specifications (IEEE 802.3 specifications) called Data Center
Bridging (DCB) enables bandwidth allocation and lossless behavior for storage traffic when the same
physical network infrastructure is shared between storage and other traffic.
The network is the fundamental resource that connects the assorted devices together to form the
datacenter Ethernet infrastructure. These devices include the server hardware (along with the
operating system and the applications that run on the host) and the storage systems that host
application data. Sharing this Ethernet infrastructure with multiple traffic types (LAN and SAN) requires
a fairness mechanism to provide bandwidth allocation and flow control for each type of traffic.
Without such a mechanism, the Local Area Network (LAN) traffic and the Storage Area Network (SAN)
traffic would have to be separated onto their own dedicated networks.
When the SAN and LAN networks are shared, all traffic is equal, unless Quality of Service (QoS) and/or
Class of Service (CoS) is used.
Traditional or Non-DCB QoS ( IEEE 802.1p) is not supported for EqualLogic implementations.
In a shared network environment, LAN and SAN traffic can impact each other and QoS may not solve
this because of QoS implementation differences with vendors. These different implementations
include:
•
Number of Queues managed
•
Relative priorities between queues
•
Bandwidth reserved per queue
Also traditional QoS lacks selective flow control for each traffic type. Regular IEEE 802.3 PAUSE will
pause the entire link and not selectively pause LAN or SAN traffic. This flow control ability is important
for reducing congestion on switches and to enable fair sharing of resources between traffic types.
Other methods of network sharing:
•
VLANs offer port-level security and segregation, but do not provide guaranteed bandwidth
or quality of service.
•
NIC partitioning (NPAR) manages traffic within the host. Once the network data exits the
NIC to the switch, any QoS/bandwidth management enforced by NPAR is not honored
by the switch.
Note: It is not recommended to share network infrastructure without DCB. DCB is the
only recommended method of converging SAN and LAN in an EqualLogic Storage
environment.
14.1 DCB Overview
DCB is a collection of Standards designed to improve QoS networking and management in the Data
Center that enables iSCSI SANs or FCoE SANs or both to converge with regular server LAN traffic on