Apple Xsan 2 (Third Edition) - Manual (Page 32)

 If you choose balance, Xsan writes data to the storage pool that has the most free
space.
Planning the Ethernet TCP/IP Network
Ethernet connections are used in several ways in an Xsan SAN:
Xsan clients and metadata controllers use Ethernet to exchange volume metadata. Â
Xsan clients can use Ethernet for access to networks outside the SAN (campus or Â
corporate intranet or the Internet).
Xsan metadata controllers can use Ethernet connections for remote management.
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RAID systems can use Ethernet connections for system management. Â
Fibre Channel switches can use Ethernet connections for switch management. Â
You have two options:
Use one Ethernet network for all traffic. This is the less expensive option, but is also Â
less secure and might not provide the best performance.
Use two separate networks—one for metadata and another for all other IP traffic.
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This configuration is slightly more expensive (requiring two Ethernet adapters for
each computer and an additional switch) but offers greater security and better
performance because routine network traffic doesn’t interfere with SAN volume
metadata traffic.
Using a Private Metadata Network
Non–SAN-related Ethernet traffic can interfere with the exchange of metadata
among Xsan controllers and clients. For example, using the same connection for Xsan
metadata exchange and Internet access can slow file system performance. Similarly,
using the same Ethernet network to connect client computers to directory services
and SAN metadata can affect SAN performance.
If SAN performance is critical for your users or applications, keep all extraneous traffic
off the network that clients and metadata controllers use to exchange metadata. For
best SAN performance, set up a private Ethernet TCP/IP network for the exclusive use
of Xsan clients and metadata controllers. For other types of network traffic, including
Internet access, RAID system and Fibre Channel switch management, remote SAN
management, or directory services, connect each client and metadata controller to a
second Ethernet network using a second Ethernet port.
Using Switches Instead of Hubs
To get the best performance, use Gigabit Ethernet switches, not hubs, in the SAN
metadata network.
32 Chapter 2 Planning a Storage Area Network