CISCO MDS SWITCHES AND DIRECTORS

Cisco's SAN solution is its Multilayer DataCenter Switches (MDS). Introduced in 2003, the MDS devices are Cisco's entry into the world of SANs and SAN management. But not only has Cisco developed its own line of gadgetry, the company has also brought some new and interesting tools, technologies, and software. In this section, we take a closer look, first, at the technologies at play behind Cisco's SAN solution. Next, we'll look at the specific hardware Cisco offers for SAN switching. Finally, you can't just hook all this hardware together and expect it to work-Cisco offers a couple of software packages to ease the configuration and management of its SANs.

Technologies

In addition to the core tools at play in SANs that we discussed in the last section, Cisco adds some other technologies to its SAN solution. While some philosophies are common with other vendors' SANs, Cisco dishes up some new ideas, like virtual SANs, trunking, and its own take on SAN security. Let's examine these technologies in more depth.

VSANs

Think back to Chapter 5 and our discussion of virtual LANs. The same sort of logic is at play behind virtual SANs (VSANs) and zones.

VSANs-which started as a proprietary Cisco technology and has since become an industry standard-allows independent, logical fabrics to be defined from a set of one or more physical switches. VSANs are isolated from other VSANs and function as a separate and independent fabric, with their own set of fabric services, like naming, zoning, routing, and so forth.

In order to transfer data traffic between VSANs, Cisco's MDS line employs a technique called inter-VSAN routing. This enables the transfer of data among sources and destinations on different VSANs, as shown in Figure 10-6, but without compromising the VSANs by merging them into a single fabric. This ensures that data can be shared between VSANs, but without affecting the VSANs' scalability, reliability, and security.

Figure 10-6: Inter-VSAN routing allows data to be transferred between VSANs but without compromising them

In addition, inter-VSAN routing works across WANs using FCIP. This allows routing features to be used across long distances, which is ideal for organizations that have their assets spread across disparate locations.

The ability to connect VSANs across a WAN link is useful, because isolated fabrics in remote data centers can be interconnected. In addition, VSANs supplement the switch's scalability and creation of multiple SAN "islands," which eliminates the need for a separate switch for different applications.

Zoning

Zoning is another method allowing limitations on users' access to storage devices. While the users are all, technically, accessing the same devices, they are only granted permission to utilize portions of specific devices. The benefit here should be obvious: security is increased and network traffic is minimized.

Zones are a segment of SAN fabric and are used to connect groups of servers with storage devices for routine processing, but can be changed as needed. For instance, the zones can be reconfigured to allow occasional backups to storage devices residing outside the individual zones. Only members of a zone have access to it.

Note 

Zone sets are groups of zones that interoperate on the fabric. Each zone set can accommodate up to 256 zones. All devices in a zone see only devices assigned to that zone, but any device in that zone can be a member of other zones in the zone set.

While it might sound like VSANs and zones are cut from the same fabric, so to speak, there is an important distinction between the two.

When using zoning, segmentation is not complete, because it takes place within the same database on the switch enforcing zones and providing addressing and routing services. A malfunctioning node on one zone can, for example, corrupt the database and cause the whole SAN to crash.

VSANs, on the other hand, are able to segment the database. As such, each defined zone is its own unique storage network with its own dedicated database. That means that if one VSAN has trouble, it doesn't affect other VSANs on the same switch.

Note 

As a reminder, a LUN is an identifier used on a SCSI bus to distinguish among devices (logical units) with the same SCSI ID.

In a SAN, storage devices are typically zoned at the device level or LUN level:

• Device level Each user is restricted to using specific devices, like RAID arrays or specific disk drives.

• LUN level This allows the administrator to allocate resources in logical units, rather than in physical units. That is, a LUN zone could be spread out over a number of physical devices. As Figure 10-7 shows, devices could easily be the home of several zones.

Figure 10-7: Zones can be configured to access resources on different devices

While zoning is a great tool for managing resources, establishing zones should not be taken lightly. Like building a house, one doesn't just stumble to the hardware store, grab a few two-by-fours, a box of nails, some shingles, and then start hammering away. Zones must be carefully planned to ensure that the best use of the SAN's storage and the network's bandwidth are considered. Additionally, once zones have been put in place, it is more difficult to move storage space from one group of users (in Zone A, for instance) to another group of users (in Zone B). If this is undertaken, it is often necessary to reboot, which will cause network disruption. Even worse, there will be security holes, since users in both zones might end up with access to the moved storage space.

QoS

Quality of Service (QoS) is an important attribute of the MDS switch line. In earlier versions of Cisco SAN-OS (we'll talk about this operating system in more detail later in this chapter), traffic was only segmented based on whether the traffic was control data or traffic data. In the most recent release of the operating system, QoS allows classification of traffic. For example, QoS can be applied so that data for latency-sensitive traffic has higher priority over throughput-sensitive applications, like data warehousing.

MDS switches provide the following QoS mechanisms:

• Priority queuing Levels of priority are assigned to different types of traffic. Latency-sensitive traffic is granted higher priority than other types of traffic.

• Fibre Channel Congestion Control (FCC) This is a flow-control mechanism used to ease congestion on FC networks. Essentially, any switch in the network can identify congestion, sample frames from the congested queue, and then send messages about the problem upstream to the source. The switch closest to the source of the congestion can either forward the frames to other switches or limit the flow of frames from the port causing the problem.

Security

As with any internetworking device or technology, security is an essential consideration. It may be especially important in SANs, where so much of your organization's data is moving around and being warehoused. The last thing you want is some thug getting into your company's archives and causing mischief.

MDS switches have a number of security features, meant to keep your data safe and secure. Let's take a closer look at the MDS switch's line of security mechanisms.

Authentication The MDS switches provide the first layer of security through its authentication methods. Authentication comes in two forms:

• User authentication Authentication, authorization, and accounting (AAA), which we talked about in Chapter 6, is used to validate users, grant access, and monitor activities. Once the user's ID and password have been sent, the switches perform local authentication, comparing the user's credentials against a local database, or remotely, using a RADIUS server.

• Switch-to-switch and host-to-switch The Cisco SAN-OS utilizes Fibre Channel Security Protocol (FC-SP) for switch-to-switch and host-to-switch authentication. This is used to stifle any disruptions that would occur if an unauthorized device tried to connect to the fabric.

Port Security Port security ensures that only an authorized device can be connected to a given switch port. Devices can be a host, target, or switch and are identified by their World Wide Number (WWN). This feature ensures that the SAN is not violated by an unauthorized device attempting connection to a switch port.

VSAN Access Control Roles can be assigned based on the limitations of a specific VSAN. For instance, the network administrator role can be authorized for configuration setup and management duties. VSAN administrators, on the other hand, can be granted permission only to configure and manage specific VSANs. This is a useful tool because it limits disruptions to the SAN. Rather than a misconfiguration affecting the entire SAN, it would be localized to the VSAN where the change was made.

Role-Based Access Going hand-in-hand with user authentication is role-based access. This mechanism limits access to the switch based on the specific permissions level granted to that user. The user can be granted full access to the device, or specific read and write levels of each command can be managed.

SPANs

A unique feature in the Cisco MDS 9000 line is the switched port analyzer (SPAN). SPAN monitors network traffic using a Fibre Channel interface. Traffic through a Fibre Channel interface can be replicated to a port known as a SPAN destination port (SD port). Any of the switch's Fibre Channel ports can be configured as SD ports. When an interface is in SD port mode, it cannot be used with normal data traffic. A Fibre Channel Analyzer can be attached to the port to monitor SPAN traffic.

As the name suggests, Remote SPAN (RSPAN) allows you to monitor traffic for SPAN sources in switches throughout a Fibre Channel fabric. The SD port of a remote switch is used for monitoring. Normally, the remote switch is different from the source switch, but is attached to the same fabric. The MDS 9000 family of switches allows the remote monitoring of traffic from any switch in the fabric as if it were the source switch.

SPAN is noninvasive, since SD ports do not receive frames; they just transmit copies of the SPAN source traffic and do not affect the redirection of network traffic. In addition, VSANs can be specified as a SPAN source. All supported interfaces in the selected VSAN are included as SPAN sources. SPAN traffic can be monitored in two directions:

• Ingress This refers to traffic entering the switch fabric through a source interface. This traffic is copied to the SD port.

• Egress This refers to traffic exiting the switch fabric through a source interface. Like the ingress traffic, this is also copied to the SD port.

When a VSAN is selected as a source, then all physical ports, as well as PortChannels, are used as SPAN sources. TE ports are included when the port VSAN of the TE port is the same as the source VSAN. TE ports are ignored if the configured allowed VSAN list has the source VSAN but the port VSAN is different.

Trunking

Harkening back to our discussion of VLANs is the term trunking. Trunking exists within the world of SANs in much the same way that it does in the world of VLANs. Trunking refers to an interswitch link (ISL) carrying more than one VSAN. Trunking ports send and receive extended ISL (EISL) frames, as shown in Figure 10-8. These frames contain an EISL header, which carries VSAN information. Once EISL is enabled on an E port, that port becomes a TE port.

Figure 10-8: Trunking in a SAN combines multiple VSAN conversations

Note 

ISL is a Cisco proprietary protocol that maintains VSAN information as traffic flows between source and destination.

PortChannel

Multiple Fibre Channel ports can be aggregated into a single, logical port, providing high aggregated bandwidth, load balancing, and link redundancy. This is known as PortChannel. This allows the aggregation of up to 16 physical ports into a single logical port.

PortChannel is a useful technology, because it increases the aggregate bandwidth on an ISL or EISL by distributing traffic among all links in the channel. Additionally, traffic is load-balanced across multiple links. This traffic is identified by source ID (SID), destination ID (DID), or the originator exchange ID (OX ID).

PortChannel also provides redundancy for its links. If one link fails, that traffic is shifted to the remaining links. Furthermore, if a link fails, the upper protocol does not perceive the link as having failed. Rather, it simply has less bandwidth with which to work. As such, the routing tables are not affected by a link failure.

Hardware

The Cisco family of MDS products includes two Cisco MDS 9500 Series Multilayer Directors, the Cisco MDS 9216i Multilayer Fabric Switch, and the Cisco MDS 9100 Series of fixed configuration switches, in addition to several modules, providing customized functionality. These devices provide intelligent network services for SANs, including VSANs, security, traffic management, diagnostics, and a centralized management environment.

Let's take a closer look at the devices in Cisco's MDS line of multilayer storage switches.

MDS 9500 MultiLayer Director Switches

The Cisco MDS 9500 MultiLayer Director switches are modular devices aimed at large datacenter environments. They provide a high level of scalability, security, and management.

The MDS 9500 Series includes three multilayer switches:

• Cisco MDS 9506 Director Targeted at datacenter environments and consisting of 192 4-Gbps ports and six slots on the chassis, two of which are reserved for supervisor modules. Four switching or services modules can be installed, providing Fibre Channel or Gigabit Ethernet services. The backplane can be directly plugged into four switching modules, two supervisor modules, two clock modules, and two power supplies.

• Cisco MDS 9509 Director Targeted at large datacenter environments, the chassis contains 336 Fibre Channel ports and nine slots, two of which are reserved for supervisor modules. Seven switching or services modules can be installed, providing Fibre Channel or Gigabit Ethernet services. The backplane can be directly plugged in to seven switching modules, two supervisor modules, two clock modules, and two power supplies.

• Cisco MDS 9513 MultiLayer Director Cisco introduced this switch in August 2002, but then pulled it off the market-turns out the world wasn't ready for this much switch. It reintroduced the switch in the spring of 2006. The Cisco MDS 9513 MultiLayer Director is a 528-port Fibre Channel device aimed at companies who want to consolidate their SANs and oversubscribing ports on smaller switches. The switch features 13 slots and 528 4-Gbps Fibre Channel ports. It also supports iSCSI and FCIP protocols.

The supervisor modules on these directors provide high-availability and loadbalancing features. A second supervisor module is available for the sake of redundancy. In addition, the autosensing Fibre Channel ports support ISL (E ports), EISL (TE ports), loop (FL and TL ports), and fabric (F ports) connections.

The Directors' small form-factor ports (SFP) are hot-swappable and can be configured for short-wavelength (500 meters) or long-wavelength (10 kilometers) connections. The ports are also individually configurable for both FCIP and iSCSI.

Table 10-2 compares the features of the Cisco MDS 9506, the MDS 9509, and the MDS 9513.

Table 10-2: Comparison of the Cisco MDS 9500 Series

	Cisco MDS 9506	Cisco MDS 9509	Cisco MDS 9513
Available Slots	6	9	13
4-Gbps Fibre Channel Ports per Chassis	192	336	528
10-Gbps Fibre Channel Ports per Chassis	16	28	44
iSCSI and FCIP Ports per Chassis	24	48	60
Rack Units	7	14	14
Chassis per Rack	6	3	3
Fibre Channel Ports per Rack	1152	1008	1584

MDS 9000 Fabric Switches

The "little brothers" to the MDS 9500 Series are the Cisco MDS 9000 switches. These use a similar architecture and software structure as the 9500 Directors. However, where the 9500s are fully modular in design, the 9000 Series is semimodular. Within this family are two series: the Cisco MDS 9216i fabric switch and the Cisco MDS 9100 Series.

Cisco MDS 9216 Multilayer Fabric Switches The Cisco MDS 9216 Multilayer Fabric Switch includes three models: the Cisco MDS 9216, the Cisco MDS 9216A, and the Cisco MDS 9216i. These switches use both Fibre Channel and IP in a single module for a strong service delivery. The switches support up to 16 2-Gbps Fibre Channel interfaces and two Gigabit Ethernet ports for FCIP and iSCSI service.

The integrated VSANs and Inter-VSAN routing allows for a large-scale, multisite SAN topology.

The ability to utilize FCIP with the MDS 9216 switches provides a number of benefits, including:

• Simplification of data protection and mission performance by enabling backup, remote replication, and other recovery services over a WAN

• Cisco MDS 9000 family capabilities are possible, including VSANs, advanced traffic management, and network security across remote connections

Benefits of iSCSI services include:

• The ability to connect to Ethernet-attached servers is much less expensive than only being able to connect through Fibre Channel

• Storage is enhanced and more widely available through the consolidation of IP and Fibre Channel block storage

The MDS 9216 switches are modular and support the line of MDS 9000 family switching or services modules outlined later in this chapter.

Cisco MDS 9020 Fabric Switch Aimed at smallto medium-sized businesses that want to build their own SANs, the Cisco MDS 9020 Fabric Switch is a 20-port Fibre Channel device offering speeds of up to 4 Gbps. Management is done through the Cisco MDS 9000 Fabric Manager and Device Manager GUI and the command-line interface (CLI), similar to IOS.

Small in its design, the Cisco MDS 9020 Fabric Switch can be used as the core of a small SAN or as an edge device in a larger SAN.

Cisco MDS 9100 Series Smalland medium-sized SANs are served with the Cisco MDS 9100 Series of Fibre Channel switches. The switches (Models 9120 and 9140) support 20 and 40 ports, respectively, and are fixed in terms of their expandability. Like their higher-powered brothers, the 9100 Series provides high levels of scalability, availability, security, and management.

The MDS 9100 Series includes built-in SAN management tools (useful for management of one or many fabric devices), including a command-line and GUI tool, which we will talk about later in this chapter.

The common architecture and software structure is an important consideration when discussing the Cisco MDS devices. Because they share a common design, it is easy to migrate from a smaller device to a larger device or to add new switches to your fabric. In addition, like any switches, the device can be purchased and installed based on a specific need within the organization.

For example, a smallto medium-sized organization can use the Cisco MDS 9120 to construct its first SAN as it moves from a direct-attached to a networked-storage solution. Larger organizations might use the 9120 for specific application or business functions.

Modules

Like many other Cisco products, the MDS 9000 family (save the 9100s) can be customized and configured based on your organization's particular needs. As such, there are a number of modules that can be installed in the devices. The following sections explain these various modules and how you can best use them in your SAN deployment.

The Cisco MDS 9500 Series Supervisor Module The Cisco MDS 9500 Series Supervisor Module provides nondisruptive software updates and hardware redundancy for optimal availability. It can automatically restart a failed process before that process is detected at the system level. This is ideal, because it reduces the number of resets to the module. However, in cases where a reset is needed, the unit's backup module will have taken over to eliminate disruption to the SAN.

With two supervisor modules installed, a 9500 Series Director can provide 1.44 Tbps of switching bandwidth. It also provides 1-, 2-, or 4-Gbps autosensing Fibre Channel ports and is compatible with future 10-Gbps modules.

Cisco MDS 9000 Family Fibre Channel Switching Modules Cisco MDS 9000 Family Fibre Channel Switching Modules are 16and 32-port devices. Each is a hot-swappable Fibre Channel trirate multiprotocol, as well as a coarse wavelength division multiplexing (CWDM) module. Individual ports can be configured with shortor long-wavelength SFPs, providing connectivity of 500 meters and 10 kilometers, respectively.

The CWDM SFP provides even great distances between devices of up to 100 kilometers. The module's interfaces operate at 1, 2, or 4 Gbps. The ports can be configured to operate as

• E ports

• F ports

• FL ports

• FX ports

• Span destination (SD) ports

• ST ports

• TE ports

• TL ports

The Cisco MDS 9000 Family IP Storage Services Module IP services can be added to the MDS 9000 family of switches through use of the Cisco MDS 9000 Family IP Storage Services Module. This module allows traffic to be routed between an IP storage port and any other port on an MDS 9000 family switch. In addition to the services available through other storage service modules (including VSANs, security, and traffic management), the Cisco MDS 9000 Family IP Storage Services Module uses IP to provide cost-effective connections to more servers and locations. This module provides FCIP and iSCSI IP storage services:

• FCIP Provides data protection by enabling backup, remote replication, and disaster recovery across WAN connections, using FCIP tunneling. WAN resources are optimally utilized by tunneling up to three ISLs on a single Gigabit Ethernet port. In addition, SAN complexity is ameliorated because a remote connectivity platform is not needed.

• iSCSI One of the best attributes of the iSCSI features of the IP storage services module is the capability to use Fibre Channel SAN-based storage to IP-based servers. This is much less expensive than just using Fibre Channel. Storage and utilization are increased because IP and Fibre Channel are consolidated for storage purposes. Furthermore, iSCSI allows the usage of legacy storage applications.

The Cisco MDS 9000 Caching Services Module Cisco teamed up with IBM to produce the Cisco MDS 9000 Caching Services Module. This module is used to virtually create a storage device from disparate storage devices around the network. This provides access to more information and is managed centrally.

This module uses two nodes that are combined with IBM's TotalStorage SAN Volume Controller Storage Software for Cisco MDS 9000, allowing network-hosted virtualization and replication.

For optimal availability and reliability, each module includes 8 GB of local cache, primary and backup batteries, and hard drives to protect data during power outages.

Software

There are two ways to manage MDS switches: from the command line or by using the Cisco MDS 9000 Fabric Manager, a GUI. The command-line interface (CLI) is similar to the CLI used for managing Cisco's other switches and routers. The GUI, on the other hand, provides a graphical representation of your SAN, its status, and the devices on the SAN. Before talking about the CLI and GUI, it's helpful to understand the operating system behind the MDS family: Cisco SAN-OS.

Cisco SAN-OS

The Cisco SAN-OS is the operating system for the Cisco MDS line of SAN devices. It provides storage networking features, including nondisruptive upgrades, multiprotocol integration, VSANs, traffic management, diagnostics, and a unified SAN management.

The latest version of the operating system, Cisco MDS 9000 SAN-OS 1.3, includes a server-based version of the Cisco Fabric Manager, an embedded graphical management tool. This inclusion provides three important improvements: centralized management of multiple fabrics; continuous health, discovery, and monitoring; and performance monitoring.

Furthermore, security in SAN-OS is enhanced through switch-to-switch and serverto-switch authentication using Fibre Channel Security Protocol (FC-SP). This protects against intrusion from unauthorized devices. It also employs TACACS+ for authentication, authorization, and accounting of switches.

CLI

The first way to manage a Cisco MDS 9000 switch is by using a serial RJ-45 connection on the supervisor module. This connection, like the connections made on other Cisco routers and switches, provides access to the CLI.

Whether you choose to use the CLI or Fabric Manager will depend largely on your personal taste and preferences. However, there are some instances when one or the other will be preferable. For example, the CLI might be optimally employed when:

• Initial setup routines are performed

• Running debug and show commands for diagnostics and troubleshooting

• Writing and running configuration scripts

When the MDS device is connected to locally for the first time, the system enters a setup routine that aids in the initial configuration of the device. This step must be completed before you are able to connect to the switch or manage it with the Cisco Fabric Manager.

The CLI parser gives command help, command completion, and the ability to access previously executed commands. Entering commands is similar to the process used when entering commands into other Cisco switches. For example, the following command would be used to send a message to all users on the network that the system will be shutting down for maintenance.

 switch# send Shutting down the system in 5 minutes. Please log off. 

To enter the configuration mode, simply enter the following on the MDS switch:

 switch# conf t switch(config)# 

Once in configuration mode, the device can be managed using a number of commands. Table 10-3 contains a brief list of some of these commands and an explanation of what they do.

Table 10-3: Several Configuration Commands Used in the CLI

Command	Description
Fcc	For configuring FC Congestion Control
Fcdomain	To enter the fcdomain configuration mode
QoS	Establishes the priority of FC control frames
radius-server	For configuring RADIUS parameters
Vsan	To enter the VSAN configuration mode
Zone	To enter zone configuration commands

The Cisco Fabric Manager

Depending on your preference, you might want to manage your MDS fabric using a graphical user interface. In this case, Cisco has provided the Cisco Fabric Manager. Fabric Manager is a Javaand SNMP-based network fabric and device management tool that shows real-time views of the fabric and installed devices. Cisco Fabric Manager is an alternative to the CLI for most switch-management operations and is included with the switches.

Cisco Fabric Manager gathers information about the fabric topology and then sends SNMP queries to the SNMP agent running on the switch to which the Fabric Manager is connected. Once the switch has discovered all connected devices, it replies. It gathers this information using data from its FSPF database, as well as from the name server database.

Fabric Manager is used to both discover and view the fabric's topology and manage zones. It is also useful for the management of:

• Zones and zone sets

• VSANs

• Port channels

• Users and roles

The GUI uses three views to manage your network fabric:

• Device View Displays a current exhibit of device configuration and performance conditions for a single device.

• Fabric View Displays the current status of the network fabric, including multiple devices.

• Summary View Displays a summary of switches, hosts, storage subsystems, and VSANs. It displays a summary of different port activity, as well as FC and IP neighbor devices.

The Cisco Fabric Manager is comprised of two network management tools supporting Simple Network Management Protocol version 3. These tools include:

• Fabric Manager Displays a map of your entire network fabric, including not only the Cisco MDS 9000 devices, but also third-party switches, hosts, and storage devices

• Device Manager Displays the Device and Summary Views of the fabric

Network-Attached Storage

NAS, which was discussed early in this chapter, is a good option for organizations that need a smaller solution and one that can run solely over IP. The crux of this chapter has been SANs, but NAS solutions certainly have their place.

Cisco introduced its Cisco FS 5500 Series Integrated NAS and Cisco FS 5700 Series Integrated NAS to provide NAS functionality. These systems support Common Internet File System (CIFS), Network File System (NFS), and File Transfer Protocol (FTP), as well as block-level storage-access protocols, including iSCSI.

These series can be used in one of two operating modes, providing either high performance or high reliability. Those modes are:

Primary/standby Designed for environments in which high availability is needed. In this configuration, one of the NAS's Data Movers operates as a stateful standby, while the other manages the movement of user requests between network and storage.

Primary/primary Designed for environments in which high performance is needed. Both Data Movers can be configured to manage information requests. If one of the Data Movers fails, the NAS will reboot within a few seconds.

Table 10-4 compares the Cisco FS 5500 Series Integrated NAS and Cisco FS 5700 Series Integrated NASs.

Table 10-4: Comparison of Cisco FS 5500 Series Integrated NAS and Cisco FS 5700 Series Integrated NASs

	Cisco FS 5500 Series	Cisco FS 5700 Series
Data Mover Configuration	Single and dual Data Mover configurations supported.	Dual Data Mover configuration only.
	Single Data Mover configurations can be upgraded nondisruptively to dual Data Mover configurations.
Data Mover CPU	Dual 1.6-GHz Pentium IV CPUs.	Dual 3.0-GHz Pentium IV CPUs.
Data Mover Memory	4-GB double data rate RAM (266 MHz).	4-GB double data rate RAM (266 MHz).
Data Mover Fibre Channel Connectivity	Two 2-Gbps ports for array/switch connectivity.	One 2-Gbps port for tape connectivity.
Ethernet Connectivity	Four 10/100/1000 ports.	Six 10/100/1000 ports (copper).
	One 10/100 management port.	Two 1000BASE-X Gigabit Ethernet ports (optical).
		One 10/100 management port.
		One 10/100/1000 management port.
Storage Processor CPU	Dual 1.6-GHz Pentium IV CPUs.	Dual 3.0-GHz Pentium IV CPUs.
Storage Processor Memory	2-GB double data rate RAM (266 MHz).	4-GB double data rate RAM (266 MHz).
Storage Processor Fibre Channel Connectivity	Two 2-Gbps ports for connectivity to Data Movers.	Two 2-Gbps ports for connectivity to Data Movers.
	Two 2-Gbps ports for connectivity to Disk Array Enclosures.	Two 2-Gbps ports for connectivity to Disk Array Enclosures.
Storage Processor Ethernet Connectivity	One 10/100BASE-T management port.	One 10/100BASE-T management port.

SANs are a burgeoning technology, and one that many organizations are expected to embrace in the coming years. While Cisco has a solid solution in its MDS line of switches, look for the company to expand its SAN offerings in the years to come. There is little doubt that there is a growing need for SANs and advanced storage, and this should be an interesting time for anyone involved in the storage arena.