Re: SCSI URL scheme [WAS: Re: iSCSI: 2.2.6. Naming & mapping]

[csapuntz@csapuntz-u1.cisco.com]

Just for clarification... I was not proposing to add the extended 
URL scheme for the transport spec. It isn't necessary.

In this thread, Doug makes an excellent point about LDAP being a
superior mechanism for describing how to connect to the
storage. Directory services such as LDAP, as Doug has pointed out,
will be critical to managing large quantities of storage. A host can
ask such a directory service for a list of storage devices it should
mount and how to connect to those storage devices. The query against
the directory server that returns this information can be based on
machine ID, user ID, operating system ID, or even the owner's
birthday. One of the things discovery will end up doing, no doubt, is
defining LDAP schemas that describe how to connect to storage
(i.e. use SCTP or TCP, what port, what target name, what LUN, what
WWN, how to authenticate, etc.).

However, there is one place where the transport protocol has to define
a name: third party commands. There needs to be some kind of global
name which the initiator can pass to the target. The name must be
distillable into a string. The target must understand the name and
be able to use the information to establish a connection to another target.

One could say that the string that is passed is not specified by the
standard but instead specified by some management software. I think
this will lead to poor interoperability.

The SCSI URL-type name is the current proposal for target name. 

Why is SCSI target name made up of a hostname + a path? Why is the
hostname + path passed on connection setup? There are two reasons.
I think NAT and IPv6 makes passing hostnames rather than addresses in
protocols more desirable. Hostnames can be re-resolved as you cross
addressing boundaries. The path is there so that the name can
support multiple targets behind a single IP address without having
to add entries to the DNS server. At Cisco, for example,
I have no control over the local DNS servers and cannot
add DNS entries for the ATAPI DVD and floppy in my computer.

_Costa