Re: Page datasets on SAN

From: Sandor W. Sklar (ssklar_at_STANFORD.EDU)
Date: 06/26/05

  • Next message: Damir Delija: "Re: Page datasets on SAN" 
    Date:         Sat, 25 Jun 2005 16:05:26 -0700
To: aix-l@Princeton.EDU

    Well, according to the EMC/IBM support matrix, booting AIX systems
    from Symmetrix or Clariion disk is supported, but I have no
    experience doing that. It does seem a bit of a catch-22, being that
    you HAVE to have a paging space in the rootvg, and yet EMC recommends
    against putting AIX paging space on SAN devices. Since I have no
    plan on booting the AIX systems from the SAN, I've never forced
    through EMC support a reconciliation of the apparent contradiction.

    We used to boot all of our Solaris systems from the Symmetrix, but as
    we moved systems to Clariion, we ran into lots of problems, and it
    just seemed as if it was more of a headache then anything else.
    We're now booting our Sun systems off of internal disk, mirrored via
    DiskSuite/SVM.

    I'd be interested in hearing the reasons why your co-worker doesn't
    like the IBM rootvg mirroring system; in my experience, I've yet to
    see any other OS do it better, either with built in tools or add on
    software.

    Good luck!
         -s-

    On Jun 24, 2005, at 10:13 AM, Vincent D'Antonio wrote:

    > based on this one would say you should never put your rootvg out
    > there? Someone here not an AIX person doesn't like the way IBM does
    > it mirroring and want to move the rootvg to the EMC disk.
    >
    > any thought's.
    > Vince
    >
    > On 6/24/05, Sandor W. Sklar <ssklar@stanford.edu> wrote:
    >
    >> We've got sort of the same problem on this issue. I've never seen an
    >> IBM document talking about this issue, but we use EMC PowerPath (with
    >> our Clariion-based SAN), and in the PowerPath 4.4 for AIX Release
    >> Notes document, it states this (on page 24):
    >>
    >> In rare cases, if the AIX swap device is stored on a CLARiiON
    >> LUN, your system may hang if all paths to the active SP are lost
    >> and the AIX code, required for PowerPath to complete a trespass
    >> operation, is swapped out of memory. If this problem occurs, you
    >> must manually trespass the LUN to the available SP and reboot
    >> the host.
    >>
    >> Unfortunately, aside from two internal drives (mirrored rootvg), the
    >> only storage on the system is Clariion, so we've had to with paging
    >> spaces on the SAN.
    >>
    >> We have had occasions where some of our AIX systems have hung
    >> (requiring hard reboot) due to a trespass issue on the SAN, but I've
    >> never been able to track down the definitive cause.
    >>
    >> -s-
    >>
    >>
    >> On Jun 24, 2005, at 7:17 AM, Holger.VanKoll@SWISSCOM.COM wrote:
    >>
    >>
    >>> you are talking about paging-spaces, dont you?
    >>>
    >>> I´ve never seen a doc from ibm that states ps on san is not
    >>> recommended and would be surprised if you could provide a link to
    >>> it.
    >>>
    >>> if "ibm says" means "somebody thats working at ibm told me..." then
    >>> you can safely ignore it. you can find others at ibm that tell the
    >>> same, and others at ibm that tell something different.
    >>>
    >>> there are ps-recommendations; in short
    >>> dont place a ps on a disk where a ps already exists
    >>> dont place a ps on a disk where a mirror of a ps already exists
    >>>
    >>> and, by far not so important
    >>> keep all ps at the same size
    >>>
    >>> the only argument against ps on san that I see is cost
    >>> if your san is less reliable than internal disks, also reliability
    >>> is of concern - if a ps is not accessible anymore, the system will
    >>> crash
    >>>
    >>>
    >>>
    >>> From: IBM AIX Discussion List [mailto:aix-l@Princeton.EDU] On
    >>> Behalf Of Morris, Carey B
    >>> Sent: Friday, June 24, 2005 3:16 PM
    >>> To: aix-l@Princeton.EDU
    >>> Subject: Page datasets on SAN
    >>>
    >>> Is anyone aware of any good white papers or redbooks regarding
    >>> placing AIX page datasets on SAN storage? IBM says it is supported
    >>> but not recommended. What is their reasoning? Performance?
    >>> Reliability?
    >>>
    >>> Thanks,
    >>> Carey Morris
    >>>
    >>
    >

  • Next message: Damir Delija: "Re: Page datasets on SAN"

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