Ultra 320 SCSI vs. 2Gb FC - HP UX

This is a discussion on Ultra 320 SCSI vs. 2Gb FC - HP UX ; I'm making a storage decision between Internal u320 SCSI and 2Gb FC. The performance of FC has been highly touted but if my math is working right it would seem to be slower, 2Gb would be 2,000,000,000/8=250,000,000 bytes per second ...

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Thread: Ultra 320 SCSI vs. 2Gb FC

  1. Ultra 320 SCSI vs. 2Gb FC

    I'm making a storage decision between Internal u320 SCSI and 2Gb FC.
    The performance of FC has been highly touted but if my math is working
    right it would seem to be slower, 2Gb would be
    2,000,000,000/8=250,000,000 bytes per second or almost 50% slower than
    320 MB/s. Can anyone offer advise on this one?


  2. Re: Ultra 320 SCSI vs. 2Gb FC

    On 2005-06-19, camattern@acm.org wrote:
    > I'm making a storage decision between Internal u320 SCSI and 2Gb FC.
    > The performance of FC has been highly touted but if my math is working
    > right it would seem to be slower, 2Gb would be
    > 2,000,000,000/8=250,000,000 bytes per second or almost 50% slower than
    > 320 MB/s. Can anyone offer advise on this one?
    >

    First of all 2Gb would be 256MB (20% slower).
    However the data on a SCSI bus is sent at U320 while the commands are sent
    at SCSI speed 5M/sec. My guess is they would probably be even.

    If you have external storage I would go to FC (due to distance and smaller
    cables). If you need internal storage I would go to SCSI since distance is
    not an issue and it's usually much more cheaper.
    In all case it's better to have 2 SCSI or 2 FC controllers for path
    redundancy (defective SCSI disks may lock the SCSI bus, FC disks I don't
    know).

    --
    weapon, n.: An index of the lack of development of a culture.
    http://www.krynos.org/ - ICQ UIN: 2295979

  3. Re: Ultra 320 SCSI vs. 2Gb FC

    Robert Pouliot wrote:
    > On 2005-06-19, camattern@acm.org wrote:
    >> I'm making a storage decision between Internal u320 SCSI and 2Gb FC.
    >> The performance of FC has been highly touted but if my math is working
    >> right it would seem to be slower, 2Gb would be
    >> 2,000,000,000/8=250,000,000 bytes per second or almost 50% slower than
    >> 320 MB/s. Can anyone offer advise on this one?


    > First of all 2Gb would be 256MB (20% slower).
    > However the data on a SCSI bus is sent at U320 while the commands are sent
    > at SCSI speed 5M/sec. My guess is they would probably be even.
    >
    > If you have external storage I would go to FC (due to distance and smaller
    > cables). If you need internal storage I would go to SCSI since distance is
    > not an issue and it's usually much more cheaper.
    > In all case it's better to have 2 SCSI or 2 FC controllers for path
    > redundancy (defective SCSI disks may lock the SCSI bus, FC disks I don't
    > know).


    I've seen a rather bad FC bus jam once, seems to me that a defective
    device can effectively lock that too. But I've only seen it happen once,
    and the field service guy claimed to never have heard of such.

    OTOH I once had a defective SCSI disk on a bus that had no members of
    the boot VG, prevent booting on HP-UX (10.20 on a H30). I kept that disk
    around for a couple of years with the intention of testing some other
    operating system's SCSI handling but never got around to doing it.


    --
    Mikko Nahkola
    #include
    #Not speaking for my employer. No warranty. YMMV.

  4. Re: Ultra 320 SCSI vs. 2Gb FC

    Mikko Nahkola wrote:

    > Robert Pouliot wrote:
    >
    >>On 2005-06-19, camattern@acm.org wrote:
    >>
    >>>I'm making a storage decision between Internal u320 SCSI and 2Gb FC.
    >>>The performance of FC has been highly touted but if my math is working
    >>>right it would seem to be slower, 2Gb would be
    >>>2,000,000,000/8=250,000,000 bytes per second or almost 50% slower than
    >>>320 MB/s. Can anyone offer advise on this one?

    >
    >
    >>First of all 2Gb would be 256MB (20% slower).
    >>However the data on a SCSI bus is sent at U320 while the commands are sent
    >>at SCSI speed 5M/sec. My guess is they would probably be even.
    >>
    >>If you have external storage I would go to FC (due to distance and smaller
    >>cables). If you need internal storage I would go to SCSI since distance is
    >>not an issue and it's usually much more cheaper.
    >>In all case it's better to have 2 SCSI or 2 FC controllers for path
    >>redundancy (defective SCSI disks may lock the SCSI bus, FC disks I don't
    >>know).

    >
    >
    > I've seen a rather bad FC bus jam once, seems to me that a defective
    > device can effectively lock that too. But I've only seen it happen once,
    > and the field service guy claimed to never have heard of such.
    >
    > OTOH I once had a defective SCSI disk on a bus that had no members of
    > the boot VG, prevent booting on HP-UX (10.20 on a H30). I kept that disk
    > around for a couple of years with the intention of testing some other
    > operating system's SCSI handling but never got around to doing it.
    >
    >

    Well an H30 was ~SCSI-2, long time ago in a land far far away -) Are
    you setting up a system for external storage or boot devices? FC with
    JBOD and JFS/LVM/VxFS is the way to go for "storage". If you need boot
    disks a pair or more of internal ultra disks will more then do the
    trick. If it is storage, can you set up a bunch of internal disks and
    stripe them with LVM or something like that? It all depends on what you
    are trying to do.

  5. Re: Ultra 320 SCSI vs. 2Gb FC

    The bigger picture of what I'm trying to do is set up affordable
    storage to meets the requirements of a business analysis tool which
    uses a back end database. Performance is tightly coupled to disk I/O
    but uptime is also a critical factor. I have access to a large SAN
    populated with Symmetrix DMX units and am leaning toward using it. My
    first step was to look at the performance differential between u320 and
    2Gb SAN. Another thought would be multiple HBA's. Could routing
    traffic via multiple paths using powerpath surpass the performance of
    u320? In other words, could I leverage 2 HBA's and powerpath to
    effectively apporach 400MB/s or will that only buy me reliability?


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