Object oriented issues

Dave.B.Anderson at seagate.com Dave.B.Anderson at seagate.com
Tue Aug 22 10:42:40 PDT 2000

* From the T10 Reflector (t10 at t10.org), posted by:
* Dave.B.Anderson at seagate.com


In the same spirit I will try to focus only on the points we have not
covered in the past.

First, I will handle the agenda issue for the upcoming SNIA WG meeting.  It
will be at the Radisson SJ on Thursday  9/7 from 8:30 to 12:00.  I hope you
can make it.

You cited the legacy SCSI stuff like mode pages that would not be needed if
an NFS-like protocl were adopted.  I guess I see it differently.  If it is
a disc drive, it will still need to support those disc-like commands,
irrespective of the read/write level of abstraction.  For instance the SEND
Diagnostic, spin up/down, etc will still be needed as well as at least some
of the mode pages.

When I mentioned that I thought an OBSD would still have to look like a
disc drive I was referring to the fact that a SCSI like protocol would be
needed.  My logic for this is that there is a company that sees the need to
support an object-like abstraction in an environment where TCP/IP and NFS
are not options.  Unfortunately,  they are not yet ready to talk about
these ideas, si I have to apologize for suggesting that I could arrange for
some material to be presented at the WG meeting in support of this

Let me know if there is anything else you need from me in order to
participate on 9/7.


p.s.  Apparently a couple of proposals for bi-directional communication
have been proposed to T10.  Gene will present a T10 summary at the WG

hafner at almaden.ibm.com on 08/16/2000 11:32:04 AM

To:   Dave.B.Anderson at Seagate.COM
cc:   snia-obsd at snia.org, t10 at t10.org

Subject:  RE: Object oriented issues


I started to write a very long winded reply to some of your comments, but I
think they are getting repetitive.

However, let me try to summarize what I think are our philosophical
differences and then summarize my position.

1) I look at an OSD as a simplified NFS, not a glorified disk drive.  You
look at it the other way around.
2) As a simplified NFS, TCP/IP is the natural protocol.  As a glorified
disk, SCSI is the natural one.

I don't deny that a SCSI specification and implementation is possible.  I
just think that it would have enormous barriers to timely standardization
and (more importantly) to pratical deployment.
TCP/IP has no fundamental architectural limitations; SCSI has many.
SCSI *might* be changed, but that will take time (both in the standards
process and in deployment of the infrastructures required to implement the
SCSI has a lot of excess baggage that isn't needed for a clean OSD model
(mode pages, to name just one).

Additionally, I don't see any point in SCSI's favor over TCP/IP in either
the short or long term .

You wrote:
> I hope that I am willing as you to be convinced otherwise.
In fact, I don't really need to be convinced at all.  There are many things
that this industry is doing that I personally am agnostic about.  If some
things are going to happen anyway and I have opinions on "implementation",
then I'll speak up.  In other words, I'll stick my nose into anything with
an opinion, but I won't try to stop anything either.  (So, if you, et al,
want to push this through T10, I'll be willing to help, even if I think
you'd be better suited to push this elsewhere.  You'll notice that I didn't
make a big deal about this point in my talk at the T10 meeting, just raised
the banner.)

>I also think your list of open issues is worthwhile.  Would be willing to
>present a summary of your paper and your position on the protocol at the
>OBSD working group meeting?
I think I can be persuaded.  Do I need to do anything in particular to get
on the agenda?

>On the question of whether an OBSD is a disc drive, I fell pretty strongly
>that it is, and I will try to line up somebody to address this at the WG
>meeting.  (It turns out that there is a lot outside of OBSD that relates
>this particular subject.)
If you're talking about packaging an OSD in something that looks like a
disk drive, that's not really the point.  The point is more how it will get
used.  An OSD's real value over a block storage device (aka disk) is in
sharing among many hosts.  That implies a network attachment.  That means
(today), two primary choices, FC (and so SCSI over FC) or ethernet (and so
IP or TCP/IP).  The physical dimensions are less important to me than the
fact that on OSD is a networked device!  Now we need to decide what's the
best network to use!

[.. deleted the rest of the history...]

Jim Hafner

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