Re: SGI Altix and Apple Xserve RAID? - SGI

This is a discussion on Re: SGI Altix and Apple Xserve RAID? - SGI ; The following header lines retained to effect attribution: >Date: Mon, 14 Jun 2004 17:39:02 +0000 (GMT) >From: "Tony 'Nicoya' Mantler" >Subject: Re: SGI Altix and Apple Xserve RAID? >To: info-iris-admin@ARL.ARMY.MIL >X-Spam-Level: >In article , Per Ekman >wrote: >: szwolfi@t-online.de (Wolfgang ...

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Thread: Re: SGI Altix and Apple Xserve RAID?

  1. Re: SGI Altix and Apple Xserve RAID?

    The following header lines retained to effect attribution:
    >Date: Mon, 14 Jun 2004 17:39:02 +0000 (GMT)
    >From: "Tony 'Nicoya' Mantler"
    >Subject: Re: SGI Altix and Apple Xserve RAID?
    >To: info-iris-admin@ARL.ARMY.MIL
    >X-Spam-Level:


    >In article , Per Ekman
    >wrote:


    >: szwolfi@t-online.de (Wolfgang Szoecs) writes:


    >: > In article ,
    >: > Atro Tossavainen writes:
    >: >
    >: > > Also, the sets the unit presents to hosts cannot consist of disks on
    >: > > more than one controller, so sets larger than 7 disks cannot exist
    >: > > natively on the controller and one must use the additional software
    >: > > RAID facilities of the host OS to combine them into larger partitions.
    >: >
    >: > so what exactly is your point here ? (technically)
    >: >
    >: > No 512 bytes/sector SCSI-LUN can EVER be larger than 2TB.


    >: Not with SBC-1, but SBC-2 allows for 64 bit LBAs, or did you mean
    >: something else?


    >For those who are interested:


    >http://www.t10.org/ftp/t10/drafts/sbc2/sbc2r14.pdf


    >See section 5, the READ/WRITE/ETC (16) and (32) commands allow 8 bytes for LBA.


    >Also, section 4.4 states:


    >"Logical block addresses are no larger than 8 bytes. Some commands support only
    >4 byte LOGICAL BLOCK ADDRESS fields (e.g., READ CAPACITY (10), READ (10), and
    >WRITE (10))."


    I would have thought that the 4 byte LOGICAL BLOCK ADDRESS fields
    for reading and writing would have been the problem.

    2^9 * 2^32 = 2^41 = 2TiB = 2199023255552B

    http://physics.nist.gov/cgi-bin/cuu/...ts/binary.html

    >And, to do the math:


    >8 bytes * 8-bit bytes = 64-bits


    >2^64 = 18446744073709551616 blocks
    >* 512 byte blocks = 9444732965739290427392 bytes


    >which is roughly 8192 exabytes, or approximately 22 billion 400 gig ATA drives,
    >or 30 billion 300 gig SCSI drives.


    >I think we're safe for a few years yet.


    >Cheers - Tony 'Nicoya' Mantler


    >Tony 'Nicoya' Mantler -- Master of Code-fu -- nicoya@ubb.ca
    >-- http://nicoya.feline.pp.se/ -- http://www.ubb.ca/ --


    Randolph J. Herber, herber@fnal.gov, +1 630 840 2966, CD/CDFTF PK-149F,
    Mail Stop 318, Fermilab, Kirk & Pine Rds., PO Box 500, Batavia, IL 60510-0500,
    USA. (Speaking for myself and not for US, US DOE, FNAL nor URA.) (Product,
    trade, or service marks herein belong to their respective owners.)

  2. Re: SGI Altix and Apple Xserve RAID?

    In article ,
    "Randolph J. Herber" wrote:

    : >http://www.t10.org/ftp/t10/drafts/sbc2/sbc2r14.pdf
    :
    : >See section 5, the READ/WRITE/ETC (16) and (32) commands allow 8 bytes for
    : >LBA.
    :
    : >Also, section 4.4 states:
    :
    : >"Logical block addresses are no larger than 8 bytes. Some commands support
    : >only
    : >4 byte LOGICAL BLOCK ADDRESS fields (e.g., READ CAPACITY (10), READ (10),
    : >and
    : >WRITE (10))."
    :
    : I would have thought that the 4 byte LOGICAL BLOCK ADDRESS fields
    : for reading and writing would have been the problem.
    :
    : 2^9 * 2^32 = 2^41 = 2TiB = 2199023255552B

    Read more closely. It is only the READ/WRITE/ETC (6), (10) and (12) commands
    that are limited.

    The (6) commands are limited to 21 bit LBAs, while the (10) and (12) commands
    are limited to 4-byte/32 bit LBAs. As I noted above, the (16) and (32) commands
    allow a full 8-byte/64-bit LBA.


    Cheers - Tony 'Nicoya' Mantler

    --
    Tony 'Nicoya' Mantler -- Master of Code-fu -- nicoya@ubb.ca
    -- http://nicoya.feline.pp.se/ -- http://www.ubb.ca/ --

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