Flexible SAN Management through Zoning Page 4


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Hard Zones

According to the Fibre Channel third-generation generic services (FC-GS-3) standard, a hard zone is defined as "a zone that is enforced by the fabric, often as a hardware function. The fabric will forward frames among zone members within a hard zone. However, the fabric prohibits frames from being forwarded to members not within a hard zone."

Hard zoning is the most secure zoning type (as with a SAN switch). The fabric enforces the hard zones and will only forward frames among other hard zone members, as the hard zone device table is created and stored at the Application-Specific Integrated Circuit (ASIC) level of the switch. In addition, a SAN switch can also support a maximum of sixty-three (63) hard zones within a fabric. Furthermore, hard zones can overlap and contain both broadcast zones and name servers. All hard zone members are defined by port number/domain.


Soft Zones

According to the FC-GS-3 standard, a soft zone "consists of zone members who are made visible to each other through client service requests. Typically, soft zones contain zone members that are visible to devices via the name server exposure of zone members. The fabric does not enforce a soft zone."

As with a SAN switch, name server zones are extremely flexible. Broadcast zones can be overlapped by name server zones. Also, all ISLs within a hard zone are available to the name server zones. Additionally, there's no maximum to the number of name server zones that can be created with a SAN switch. For example, the newest ANSI standards identify three member-address schemes that are used in name server zoning:


  • Fibre Channel Address (FCA)
  • Port
  • World wide name (WWN)

Thus, each address member can coexist in the same zone.


Summary And Conclusions

SAN switch zoning capabilities and naming conventions help storage managers make informed decisions regarding their switch purchases. In order to easily create and manage SANs that include both private and public devices, Fibre Channel switches should be added to Storage Area Networks (SANs) to give storage managers tremendous flexibility. The switch's capability to create zones is the key to these highly flexible, manageable SANs or partitions within the total SAN fabric.

It is also important to understand how zoning is accomplished within the fabric as storage managers evaluate switches from various vendors. Fibre Channel switch vendors developed their own naming conventions and features prior to the Fibre Channel Switch Fabric second generation (FC-SW-2) specification. Now that the FC-SW-2 specification has been completed and approved, any switch that is fully FC-SW-2 compliant will coexist in a SAN fabric, regardless of the vendor.

John Vacca is an information technology consultant and internationally known author based in Pomeroy, Ohio. Since 1982, John has authored 39 books and more than 485 articles in the areas of advanced storage, computer security and aerospace technology. John was also a configuration management specialist, computer specialist, and the computer security official for NASA's space station program (Freedom) and the International Space Station Program, from 1988 until his early retirement from NASA in 1995. John was also one of the security consultants for the MGM movie titled : "AntiTrust," which was released on January 12, 2001. John can be reached on the Internet at jvacca@hti.net.


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