2 TByte Barrier

David Ford dford at orca.com
Wed May 12 13:44:14 PDT 1999

* From the T10 Reflector (t10 at symbios.com), posted by:
* David Ford <dford at orca.com>
Hi George.

I'm not sure I see a problem here. The 6 TBytes of quoted capacity for the 
Hitachi subsystem is for a Target which supports multiple LUNs. Assuming 
Hitachi supports at least 8 LUNs per Target (256 is more likely), there's 
no problem. Since we have an 8 byte LUN field, I don't see a problem until 
well into the next millennium. I also don't see a need to support a single 
LUN larger than 2 TBytes. Is anyone really asking for this?

--Dave Ford

At 09:19 AM 5/12/99 , gop at us.ibm.com wrote:
>* From the T10 Reflector (t10 at symbios.com), posted by:
>* gop at us.ibm.com
>The following is an announcement from Hitachi that indicates their new 
>supports a maximum capacity of 6 TBytes. I am sure this is only the first of
>many subsystems that will exceed  the 2 TBytes capacity.  This is a 
>problem for
>SCSI because the largest LBA possible with in current block commands is a four
>byte value. Assuming a block size of 512 bytes the current LBA provides only
>enough addressing for 2 TBytes of information. Of course there are ways around
>this; making the block size larger, chopping the subsystem into smaller 
>volumes, etc. but those are not necessarily the best solutions.
>What the SCSI committee needs to do is create a set of block commands that 
>us beyond 4 byte LBAs. But to do this we need to start a SBC-2 project and 
>to do
>that we need an editor.
> >From IBMs point of view this is something that has been simmering in the
>background for some time that is rapidly becoming a major issue that needs a
>solution before someone invents a proprietary solution that no one likes but
>that we will be forced to implement.
>Hitachi Data Systems Announces New 36 GB And 15 GB Disk Drive Options for
>Freedom Storage 7700E Subsystem
>Business Wire, SANTA CLARA, Calif., May 10, 1999 -- New Drive Boosts Maximum
>Subsystem Capacity to 6 TB; Contributes to Lower Cost of Operation -- 
>the range of choices available to customers who wish to optimize the capacity
>and performance of their storage subsystems, Hitachi Data Systems today
>announced two new disk drive options for its flagship subsystem, the
>multi-platform Hitachi Data Systems(R) Freedom Storage(tm) 7700E.
>The company will now offer 36 gigabyte (GB) and 15 GB disk drives with the
>Freedom 7700E storage subsystem.
>Doubling the maximum capacity of the Freedom 7700E to 6 terabytes (TB), use of
>the new 36 GB disk drive enables customers to spread the controller cost 
>over a
>much larger subsystem capacity, providing a substantial reduction in the total
>cost of operation.
>The Freedom 7700E can be configured as a high-performance or high-capacity
>solution. Using the 36-gigabyte disk drive, 7700E customers will be able to
>achieve good performance at the lowest cost per byte. For applications that
>require higher performance, customers can use the new 15 GB disk drive -- the
>fastest commercially available drive in the world, spinning at more than 
>revolutions per minute -- to implement a configuration with up to 2.5 TB in a
>single Freedom 7700E subsystem.
>The 36 GB and 15 GB disk drives can be intermixed with the 18 GB and 6 GB disk
>drive options currently offered with the Freedom 7700E. The new 36 GB and 15GB
>disk drives are available immediately.
>Bye for now,
>George Penokie
>Dept PPV  114-2 N212
>E-Mail:    gop at us.ibm.com
>Internal:  553-5208
>External: 507-253-5208   FAX: 507-253-2880
>* For T10 Reflector information, send a message with
>* 'info t10' (no quotes) in the message body to majordomo at symbios.com

     Dave Ford                                            Orca Systems
     dford at orca.com                                       77 Union St.
     617-926-1399                                 Watertown, MA. 02172

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