ESN Manager performs two main functions, zoning and LUN masking. Zoning allows hosts and fibre adaptor ports (FAs) to be grouped together for access. An HBA (host bus adaptor) can be a member of multiple zones as can an FA. Our zoning standard is to restrict a zone to having one HBA member and one FA member, although this is not strictly necessary. Our zoning information is held under ESN Manager in the fibrezone database, a flat file database mapping out switches, hosts, zones and fabrics. LUN masking restricts individual LUNs (actual disk devices) to a specific HBA where an FA is shared by multiple hosts. LUN masking is a feature of the disk subsystem. EMC refers to its LUN masking by the product that was used to manage the process, Volume Logix. Details of LUN masking are stored in the Volume Logix database, a pseudo device visible on each FA port. Changes to zoning are made using the fzone command. This amends the fibrezone database. Changes can then be distributed to the fabric infrastructure (a fabric refresh). Changes to LUN masking are made using the fpath command. This makes immediate changes to LUN masking. Let's look first at fzone. Fzone sub-commands operate on five entity types; members, zones, zone sets, interfaces and units. Three other subcommands operate on the fabric (for performing refreshes), admin commands (backup/restore of the database) and obtaining version information. The entities are: • Member - host bus adaptors and FAs for non-EMC disk subsystems. • Zone - SAN zones. • Zone_Set - a group of zones that is active on a fabric. • Interface - manufacturer devices managed by ESN Manager. • Unit - a switch. It is unlikely that you would want to change an interface, and very rarely zone sets, so we will concentrate on members, units and zones. Units Use the fzone unit subcommands to list, modify and create new units within the configuration. All units are given an index number and a local name. You can perform most operations using either name or index number. For example, the following shows the output from an -info sub-command, which displays details on a single switch.
C:\WINNT\ fzone unit -info 1

id = 1 name = switch1 type = unit in use = no unit type = std zone set = UNIX2 zoning = enabled refreshed = yes (Fri Jul 18 14:28:23 2003) default zone = OFF member of = interface = Mcdata conn. data = ip=163.2.56.109,wwn=10:00:08:00:88:a0:aa:44
Zones Use the fzone zone subcommands to list, modify and create new zones. All zones are given an index number and a number. Zones have members (which have been explained previously). When creating a new zone, the zone name and members of the zone are specified. See the output below on listing zone information.
C:\WINNT\Profiles\evansc>fzone zone -info 3

id = 3 name = Test_Zone type = zone in use = yes members = member_5,member_6 zone set = DISTRIBUTED2
Members Members are individual host bus adaptors (or non-EMC disk subsystems). Each member has an index number, name and a unique WWN (world-wide name). Members can be associated with one or more zones. This can be seen in the output from an fzone member -info command.
C:\WINNT\>fzone member -info 3

id = 3 name = member_3 type = member in use = yes wwn/port-id = 21:00:00:E0:8B:07:D9:8D node wwn = device type = UNKNOWN zones = Test_ZONE, Production_ZONE
Managing Changes All fzone sub-commands that modify entity information operate only on the fibrezone database. Changes are not made to the switches in a fabric until an fzone fabric refresh command is issued. This distributes the current fibrezone configuration to the entire list of switches in the database, or to individual switches and fabrics, if they are specified on the command. In order to manage changes to the environment, the fibrezone database can be backed up. The fzone admin -backup command writes the entire configuration to a specified file. The file is simply a concatenation of the individual database files that make up the fibrezone database. A backup copy can be restored into an existing fibrezone database, should this be required. Our internal process for making modifications to the SAN environment requires that we take a copy of the fibrezone database before we make any zoning changes. That way, if you have any issues, you have a clear backup plan. Additionally, keep a remote server at your disaster recovery site for use in an emergency. With a current backup of the fibrezone database, you can be sure you are working with the latest configuration. In the next article we will look at fpath commands and interrogating the Volume Logix database.