Re: SGI Altix and Apple Xserve RAID? - SGI

This is a discussion on Re: SGI Altix and Apple Xserve RAID? - SGI ; Tony 'Nicoya' Mantler wrote: > In article , > rblander@mfcf.math.uwaterloo.ca (Robyn Landers) wrote: > > : Have any of you used the Apple Xserve RAID with an SGI Altix? > You should be aware, of course, that the Xserve RAID ...

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Thread: Re: SGI Altix and Apple Xserve RAID?

  1. Re: SGI Altix and Apple Xserve RAID?

    Tony 'Nicoya' Mantler wrote:

    > In article ,
    > rblander@mfcf.math.uwaterloo.ca (Robyn Landers) wrote:
    >
    > : Have any of you used the Apple Xserve RAID with an SGI Altix?


    > You should be aware, of course, that the Xserve RAID is an FC/ATA system,
    > where as most RAIDS are either FC/SCSI or FC/FC. This will restrict you to
    > using cheaper, slower (in latency terms) ATA drives, which you should keep
    > in mind when evaluating the product.
    >

    The default drives that Apple ship in the drive modules are 7200RPM too,
    which may be a bit sucky for many people. I'm not sure of the "take 'em
    out and replace 'em" options. Oh, and point of pedantry: it's FC/SATA ;-)

    --
    Graham Lee
    I am leeg, for we are many
    Real programmers don't document. If it was hard to write, it's going to be
    hard to understand.
    http://users.ox.ac.uk/~wadh1342


  2. Re: SGI Altix and Apple Xserve RAID?

    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.
    (AFAIK some Cipricos have the option for 4kbytes/sector => 16 TB LUN,
    but the Xserve is 512 bytes/sector only.)
    So whatever capacity you buy with the Xserve - above 2TB
    you always have to have at least 2 LUNs.

    wolfgang

  3. Re: SGI Altix and Apple Xserve RAID?

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

    > so what exactly is your point here ? (technically)
    >
    > No 512 bytes/sector SCSI-LUN can EVER be larger than 2TB.


    You're obviously smarter and better read than I am and thought of
    something that didn't even occur to me. Thanks for pointing that out.

    --
    Atro Tossavainen (Mr.) / The Institute of Biotechnology at
    Systems Analyst, Techno-Amish & / the University of Helsinki, Finland,
    +358-9-19158939 UNIX Dinosaur / employs me, but my opinions are my own.
    < URL : http : / / www . helsinki . fi / %7E atossava / > NO FILE ATTACHMENTS

  4. Re: SGI Altix and Apple Xserve RAID?

    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?

    *p

  5. Re: SGI Altix and Apple Xserve RAID?

    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))."

    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/ --

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