iSNS scalability

[Ernest Dainow <Ernest.Dainow@mcdata.com>]

A major motive for the use of iSNS is to provide scalability in a storage
network. While many of the proposed features of iSNS do provide this, it
falls short in a few areas.

An organization with storage at several locations should have the option for
local management by each site, with an easy method to share storage between
sites. This is also required for sharing resources between organizations,
such as between business partners or between a Storage Service Provider and
customers. 

iSNS (draft 8) addresses this somewhat in Section 3.7, "Transfer of iSNS
Database Records between iSNS Servers". However, the mechanism suggested for
doing this may not be straight forward to automate and may require manual
intervention between sites to keep multiple iSNS servers synchronized. In
addition, since the mechanisms are suggested and not standardized, there
will probably not be a high degree of interoperabilty between different
implementations of iSNS.

The best example of a well-proven, scalable architecture to address this is
the Internet Domain Name Services (DNS). DNS scales from single-site to
multi-site to the global Internet. The key DNS concept lacking in iSNS is
that of local authority (i.e. ownership). With DNS, a site has authority for
its own domains. Requests for information about its domain are supplied by
its own servers (primary or secondary). When a server's domain name records
are modified, its database does not need to be replicated or synchronized
with external DNS servers. 

So, for example, in an organizaton global.com, there might be subdomains
partitioned and managed by different regions of the company, such as
us.global.com and europe.global.com. A region can further partition its
domain if desired,  into say london.europe.global.com,
rome.europe.global.com, etc. 

The concept of local authority, as used in DNS, could be applied to iSNS
objects such as Storage Nodes and Discovery Domains. That is, only one iSNS
server would maintain authoritative records for a particular object. A
hierarchical iSNS with local authority would add significantly to the
scalability of IP storage.