Multi-Node Clusters; Zoning - Compaq BL10e - HP ProLiant - 512 MB RAM Manual

Multi-node clusters

A multi-node cluster using SAS provides an alternative to clustered Fibre Channel local loop
topologies. This highly scalable SAS architecture enables topologies that provide high performance
and high availability with no single point of failure. Figure 12 shows a multi-node cluster application
using a SAS RAID HBA controller. This SAS topology can also be implemented using an ASIC
(application-specific integrated circuit) embedded on the motherboard.
Figure 12. Topologies for multi-node cluster applications using a SAS RAID controller provide high performance
and high availability.

Zoning

The number of devices (initiators, targets, expanders, and/or virtual devices) allowed in a given
domain is limited only by the size of the expander routing tables. But managing such a large number
of devices can be very complicated. Therefore, zoning was introduced into the SAS-2 standard for
efficiency (traffic management) and security. With SAS-2, large physical topologies can be broken
into logical groups. This grouping allows access within and between zone groups being controlled. A
group of zoning-enabled expanders that cooperate to control access between phys is known as a
zoned portion of a service delivery system (ZPSDS).
There can be 128 or 256 zone groups numbered from 0 to 127 or 0 to 255, respectively. Zone
groups 0 through 8 are pre-defined and cannot be changed by the user. Devices in zone group 0 can
only access devices in zone group 1, while devices in zone group 1 are allowed access to all zone
groups. For example, a system administrator can use zone group 0 for a new (unassigned) device
that is added to a ZPSDS. At the same time, the administrator can use zone group 1 for topology
discovery and zone management.
Permission tables in SAS expanders control zoning. This means that an end device does not require
any special features to operate within a zoned SAS domain, which makes legacy SAS and SATA
devices compatible. An end device in a zone can only ―see‖ other end devices in the domain as
permitted by the zoning expander(s). Figure 13 shows a SAS domain with a ZPSDS containing three
zoning expanders in addition to one expander device without zoning enabled.
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