Subject: RE: I-D ACTION:draft-ietf-ips-scsi-mib-04.txt

From: "Amir Shalit" <[email-masked]>
Date: Wed, 30 Oct 2002 09:58:47 -0800

I have two comments:

1) Read/Write counters

Counter32 (counting MB transferred) wrap at about 1000 hours on 10Gbps
links. 
Can we the MIB use a Counter64 instead?

2) Virtualization 

An attempt was made to list all LU's which are part of a LUN.
In my opinion, the ultimate mechanism to represent hierarchical volumes
is via a volume manager MIB. For the time being it will be useful to
associate a {start LBA, end LBA} vector with each LU to allow for most
simplistic virtualization mapping.

Amir

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] 
Sent: Wednesday, October 30, 2002 3:20 AM
Cc: [email-masked]
Subject: I-D ACTION:draft-ietf-ips-scsi-mib-04.txt

A New Internet-Draft is available from the on-line Internet-Drafts
directories. This draft is a work item of the IP Storage Working Group
of the IETF.

	Title		: Definition of Managed Objects for SCSI
Entities
	Author(s)	: M. Hallak-Stamler, M. Bakke et al.
	Filename	: draft-ietf-ips-scsi-mib-04.txt
	Pages		: 73
	Date		: 2002-10-29
	
This memo defines a Management Information Base (MIB) for Small 
Computer System Interface (SCSI) entities, independently of the 
interconnect subsystem layer.

A URL for this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-ietf-ips-scsi-mib-04.txt

To remove yourself from the IETF Announcement list, send a message to 
ietf-announce-request with the word unsubscribe in the body of the
message.

Internet-Drafts are also available by anonymous FTP. Login with the
username "anonymous" and a password of your e-mail address. After
logging in, type "cd internet-drafts" and then
	"get draft-ietf-ips-scsi-mib-04.txt".

A list of Internet-Drafts directories can be found in
http://www.ietf.org/shadow.html 
or ftp://ftp.ietf.org/ietf/1shadow-sites.txt

Internet-Drafts can also be obtained by e-mail.

Send a message to:
	[email-masked].
In the body type:
	"FILE /internet-drafts/draft-ietf-ips-scsi-mib-04.txt".
	
NOTE:	The mail server at ietf.org can return the document in
	MIME-encoded form by using the "mpack" utility.  To use this
	feature, insert the command "ENCODING mime" before the "FILE"
	command.  To decode the response(s), you will need "munpack" or
	a MIME-compliant mail reader.  Different MIME-compliant mail
readers
	exhibit different behavior, especially when dealing with
	"multipart" MIME messages (i.e. documents which have been split
	up into multiple messages), so check your local documentation on
	how to manipulate these messages.

Below is the data which will enable a MIME compliant mail reader
implementation to automatically retrieve the ASCII version of the
Internet-Draft.

---

From: Paul Koning <[email-masked]>
Date: Wed, 30 Oct 2002 13:59:03 -0500

>>>>> "Amir" == Amir Shalit <[email-masked]> writes:

 Amir> I have two comments: 1) Read/Write counters

 Amir> Counter32 (counting MB transferred) wrap at about 1000 hours on
 Amir> 10Gbps links. Can we the MIB use a Counter64 instead?

Makes sense to me.

 Amir> 2) Virtualization

 Amir> An attempt was made to list all LU's which are part of a LUN.
 Amir> In my opinion, the ultimate mechanism to represent hierarchical
 Amir> volumes is via a volume manager MIB. For the time being it will
 Amir> be useful to associate a {start LBA, end LBA} vector with each
 Amir> LU to allow for most simplistic virtualization mapping.

I don't like this idea at all.  Let's keep that stuff out of this MIB.

  paul

---

From: Bill Studenmund <[email-masked]>
Date: Wed, 30 Oct 2002 12:11:40 -0800 (PST)

> Can we the MIB use a Counter64 instead?

Why?

Looking at the description of Countter64 in _Understanding_SNMP_MIBs_ by
Perkins & McGinnis, page 47, middle of "behavior" paragraph, "This type
may only be used when a 32-bit counter rollover could occur in less than
an hour. Otherwise the Counter32 type must be used."

While that book isn't an RFC, the authors know a lot about SNMP. I doubt
they would write the above if it weren't standard policy.

Looking at my copy of SNMPv2-SMI.txt, I also find:

-- for counters that wrap in less than one hour with only 32 bits
Counter64 ::=
    [APPLICATION 6]
        IMPLICIT INTEGER (0..18446744073709551615)

Digging around some more, in section 7.1.11of RFC 1442 (SMI for SNMPv2):

          A requirement on "standard" MIB modules is that the Counter64
          type may be used only if the information being modeled would
          wrap in less than one hour if the Counter32 type was used
          instead.

So since 1000 hours >> 1 hour, looks like RFC 1442 says, no we can't use a
counter64.

Take care,

Bill