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    RE: iSCSI has already been done before, sort of...



    It's not clear to me what the point of this message is,
    since the author says:
    
    > Right up front, this is **NOT** proposed as a protocol for adoption but it
    > does offer to us some valuable insights in how to handle some of the
    > questions at hand.
    
    but then has very little to say in terms of exactly
    what the insights are.  The bullet list of IPI-3 features
    isn't particularly helpful; is the intent to put them
    forward as requirements?
    
    Could I suggest writing an Internet-Draft on the topic of
    what the author thinks is wrong with iSCSI, why, and how to
    fix it as a productive alternative to making disparaging
    comments on the efforts of others?
    
    --David (future WG co-chair)
    
    ---------------------------------------------------
    David L. Black, Senior Technologist
    EMC Corporation, 42 South St., Hopkinton, MA  01748
    +1 (508) 435-1000 x75140, FAX: +1 (508) 497-6909
    black_david@emc.com  Cellular: +1 (978) 394-7754
    ---------------------------------------------------
    
    
    > -----Original Message-----
    > From:	Bill Main [SMTP:wmain@gis.net]
    > Sent:	Friday, July 07, 2000 10:13 AM
    > To:	ipSCSI list
    > Subject:	iSCSI has already been done before, sort of...
    > 
    > Folks-
    >     If this seems late in the cycle, I apologize but I just recently
    > joined this project and I realize there is an IETF deadline looming
    > but....
    > 
    >     How does the adage go? Those who fail to learn from history are
    > doomed to repeat it.
    > 
    > That I believe applies here. Many protocols have been put forward or
    > mentioned but one seems distinctly absent from this discussion. Right up
    > front, this is **NOT** proposed as a protocol for adoption but it does
    > offer to us some valuable insights in how to handle some of the
    > questions at hand.
    > 
    > The important thing is that it does everything iSCSI is trying to do and
    > it has been running for years at performance levels that iSCSI will
    > struggle to match.
    > 
    > Here are some of its features:
    > 
    > - Been around a long time (not well known even though has an ANSI spec)
    > - Specs revised and improved 1986, 92, 95 and latest twik to spec in 97
    > - Up and running and supported by IBM, Compaq(Digital), NEC, Cray and
    > SGI & probably others.
    > - Connects large storage farms to hosts over switched network
    > - Deals well with congestion delays
    > - Handles tapes
    > - works with all common unix host based file systems.
    > - priority classifications for what now is called QoS.
    > - adaptable block size on transmit
    > - allows coalescing of data for transfer (sorts transmit queue to
    > optimize transfers)
    > - Designed and built to function on full duplex 100 MB/s networks albeit
    > LAN only.
    > - Optional multiple path capability for load balancing or striping for
    > both hosts and targets.
    > - Optional out of band command and response channel (usually Ethernet).
    > - Header layout done so receiver has a priori knowledge of pay load and
    > can segregate address data such that payload goes to page flip memory
    > (Does exactly what RDMA wants to do).
    > - Has a transmit credit system.
    > - Sports a well thought out error and recovery system (this could be
    > very useful)
    > - Handles partition, spanning and volume work.
    > - Performance numbers are commonly in the range of 85MB/s raw and 50
    > MB/s with a file system (WRITE) on single path with in line command and
    > response using 8KB file blocks. The 50 is a file system limitation
    > regardless of storage system class.
    > - relatively easy to implement, only about 1.5 man-years to get it
    > designed, coded and working into production envirnoment
    > - has stages of operation that are very SMP (or ASIC) friendly
    > 
    > 
    > It is called IPI-3 and runs currently only over Hippi networks which are
    > as close to being a SAN as any FC layout. Specs are available from the
    > T11 group (http://www.t11.org/index.html)
    > Grab the IPI-3DR and IPI-3TR versions (disk and tape respectively).
    > 
    >     Having been the original architect on one implementation of IPI-3,
    > there is a lot of knowledge in there that has been stepwise improved on
    > over the 14 years of its existence, but it does exactly what iSCSI is
    > trying to do.
    > 
    >  Now the bad news: Does not use IP or TCP but IPI-3 is very efficient.
    > Note though, the Hippi-PH can be replaced by IP if one really wanted to
    > without much effort.
    > 
    >  First, from my perspective it appears that iSCSI is a re-invention of
    > the wheel - Not that a redesigned wheel can't be made better. But it
    > always seemed better to study the original while doing it.
    > 
    >  Second, when you pull the specs, you will notice that they are weighty.
    > Having designed an implementation of a network disk transfer system (ala
    > iSCSI) for IPI-3, I assure you there is very little excess in there.
    > Eventually every issue that generated paragraphs in the IPI-3 spec will
    > show up in the iSCSI implementations as well.
    > 
    >  Regards,
    >     Bill Main
    > 
    
    


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Last updated: Tue Sep 04 01:08:10 2001
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