How to Mirror data vg - Aix

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  1. How to Mirror data vg

    Looking for a little help mirroring a data vg

    I have a total of 4 disks.
    I want to create a vg with two of the disks and use the other 2 for
    the mirror.

    Thanks!

  2. Re: How to Mirror data vg

    MC Pee pants schrieb:
    > Looking for a little help mirroring a data vg
    >
    > I have a total of 4 disks.
    > I want to create a vg with two of the disks and use the other 2 for
    > the mirror.


    there is no mirroring of disks (== physical volume) in AIX' volume
    manager. You can mirror the hardware by the means of a hardware RAID
    controller.

    In AIX you add the free physical volumes into the data vg and then add a
    copy to each logical volume onto the free physical volume.

    The command "mirrorvg" does the adding of copies of the logical volumes
    with one command.

    The command "extendvg" adds a free physical volume into an existing
    volume group

    --
    Uli Link

  3. Re: How to Mirror data vg

    Uli Link schrieb:
    > MC Pee pants schrieb:
    >
    >> Looking for a little help mirroring a data vg
    >>
    >> I have a total of 4 disks.
    >> I want to create a vg with two of the disks and use the other 2 for
    >> the mirror.

    >
    >
    > there is no mirroring of disks (== physical volume) in AIX' volume
    > manager. You can mirror the hardware by the means of a hardware RAID
    > controller.


    huh ?
    Maybe it's nitpicking or a matter of wording,
    but I always "mirror" the rootvg (and other important
    volumes) using two disks.
    As secure but simpler than RAID, IMHO.

    The OP wants sth different, i.e. first combining
    two small disks into a bigger one, and than
    "mirroring" the result onto the second set of small disks.
    I'm not sure how this can be done.


  4. Re: How to Mirror data vg

    Michael Kraemer schrieb:
    > Uli Link schrieb:
    >> MC Pee pants schrieb:
    >>
    >>> Looking for a little help mirroring a data vg
    >>>
    >>> I have a total of 4 disks.
    >>> I want to create a vg with two of the disks and use the other 2 for
    >>> the mirror.

    >>
    >>
    >> there is no mirroring of disks (== physical volume) in AIX' volume
    >> manager. You can mirror the hardware by the means of a hardware RAID
    >> controller.

    >
    > huh ?
    > Maybe it's nitpicking or a matter of wording,
    > but I always "mirror" the rootvg (and other important
    > volumes) using two disks.
    > As secure but simpler than RAID, IMHO.


    the mirroring is "only" at lv level. If you mirror your boot logical
    volume you have to call "bosboot -a" so that the mirrored boot volume
    can be booted too. If not the bootsector isn't mirrored. It's outside
    the lv's. Small differnce may be important in case of rootvg.
    Should not matter for any data vg.

    > The OP wants sth different, i.e. first combining
    > two small disks into a bigger one, and than
    > "mirroring" the result onto the second set of small disks.
    > I'm not sure how this can be done.
    >


    migratepv the lv's from the small disks a bigger one.
    I always started with adding a copy of the jfs journal lv to the target
    disk so there is free diskspace in the center zone. Then migratepv the
    other lv's one by one until the source disk only contains a copy of the
    journal lv. Then remove this copy and reducevg. The now empty source
    disk can be deconfigured, llformatted or removed.
    I remember once running into trouble with inconsistencies between
    filesystem and journal be "migratepv"ing the journal lv too. Since then
    I always did it the add copy/remove copy way.
    If the new disk contains a boot lv update the bootlist and run "bosboot -a"

    --
    Uli Link

  5. Re: How to Mirror data vg

    Michael Kraemer pisze:
    > Uli Link schrieb:
    >> MC Pee pants schrieb:
    >>
    >>> Looking for a little help mirroring a data vg
    >>>
    >>> I have a total of 4 disks.
    >>> I want to create a vg with two of the disks and use the other 2 for
    >>> the mirror.

    >>
    >>
    >> there is no mirroring of disks (== physical volume) in AIX' volume
    >> manager. You can mirror the hardware by the means of a hardware RAID
    >> controller.

    >
    > huh ?
    > Maybe it's nitpicking or a matter of wording,
    > but I always "mirror" the rootvg (and other important
    > volumes) using two disks.
    > As secure but simpler than RAID, IMHO.


    software RAID is NEVER as secured as HW RAID. Who told you that?
    Electronics functions of contollers are more sophisticated and created
    according to XOR algorithms...

    > The OP wants sth different, i.e. first combining
    > two small disks into a bigger one, and than
    > "mirroring" the result onto the second set of small disks.
    > I'm not sure how this can be done.
    >

    I think he's asking for advices about disk-disk mirror into AIX LVM. I
    belive that simplest think will be create 4 disk VG and done mirror for
    LV's.

    Rgrds,
    Blazej

  6. Re: How to Mirror data vg

    In article , Blazej Antczak
    writes:

    >
    > software RAID is NEVER as secured as HW RAID. Who told you that?


    Experience tells me that almost always those devices
    tend to fail which contain spinning parts, i.e. disks and fans.
    So for a rootvg I always found it sufficient to connect two disks
    to the internal controller,
    mirror them (plus two times "bosboot -a" to enable boot sectors).
    Worked just fine for well over a decade now :-)

    > Electronics functions of contollers are more sophisticated and created
    > according to XOR algorithms...


    keep it small, keep it simple ...


    > I think he's asking for advices about disk-disk mirror into AIX LVM. I
    > belive that simplest think will be create 4 disk VG and done mirror for
    > LV's.


    Mirroring hdisk0 onto hdisk1 is almost trivial.
    As is creating a larger "virtual disk" (hdisk0,hdisk1) from two smaller ones.
    What he seems to ask for is how to mirror (hdisk0,hdisk1)
    onto a second "virtual disk" (hdisk2,hdisk3).

  7. Re: How to Mirror data vg

    Michael Kraemer schrieb:

    >> Electronics functions of contollers are more sophisticated and created
    >> according to XOR algorithms...

    >
    > keep it small, keep it simple ...
    >


    Oh jes. I've got quite a lot failed hardware raid controller under my
    fingers. Never had any real problems with any UNIX' volume manager.
    Regardless Veritas on NCR MP-RAS, Solaris or HP-UX or AIX' lvm (which is
    the very best of it's kind).

    >> I think he's asking for advices about disk-disk mirror into AIX LVM. I
    >> belive that simplest think will be create 4 disk VG and done mirror for
    >> LV's.

    >
    > Mirroring hdisk0 onto hdisk1 is almost trivial.
    > As is creating a larger "virtual disk" (hdisk0,hdisk1) from two smaller ones.
    > What he seems to ask for is how to mirror (hdisk0,hdisk1)
    > onto a second "virtual disk" (hdisk2,hdisk3).


    Any mirror copies of a given lv must live in the same volume group,
    though you can have many volume groups. Any physical disk can only
    belong to zero or exactly one vg. A lv can spread over more than one
    physical volume.
    Theoretically you can add mirror copies onto the same physical volume,
    but this is a very bad idea.

    There is no intermediate level of virtual disk between lv and vg like a
    group of lv's.

    --
    Uli Link


  8. Re: How to Mirror data vg

    Michael Kraemer pisze:
    > In article , Blazej Antczak
    > writes:
    >
    >> software RAID is NEVER as secured as HW RAID. Who told you that?

    >
    > Experience tells me that almost always those devices
    > tend to fail which contain spinning parts, i.e. disks and fans.
    > So for a rootvg I always found it sufficient to connect two disks
    > to the internal controller,
    > mirror them (plus two times "bosboot -a" to enable boot sectors).
    > Worked just fine for well over a decade now :-)
    >

    yep, its working - but still will work on controller w/RAID functions
    implemented. I'm not talking about JBOD's or disk arrays )

    >> Electronics functions of contollers are more sophisticated and created
    >> according to XOR algorithms...

    >
    > keep it small, keep it simple ...
    >

    TRUE

    >
    >> I think he's asking for advices about disk-disk mirror into AIX LVM. I
    >> belive that simplest think will be create 4 disk VG and done mirror for
    >> LV's.

    >
    > Mirroring hdisk0 onto hdisk1 is almost trivial.
    > As is creating a larger "virtual disk" (hdisk0,hdisk1) from two smaller ones.
    > What he seems to ask for is how to mirror (hdisk0,hdisk1)
    > onto a second "virtual disk" (hdisk2,hdisk3).

    Yes - there's always problem with not-exact asked questions. So best
    answer is the most popular in IT answer: ...Depends...

  9. Re: How to Mirror data vg

    MC Pee pants wrote:
    > Looking for a little help mirroring a data vg
    >
    > I have a total of 4 disks.
    > I want to create a vg with two of the disks and use the other 2 for
    > the mirror.
    >
    > Thanks!


    Generally speaking, I assume you saying you're saying the LVs/FSs you're
    planning to add will be large enough to be held on 2 disks, and that
    once that VG is built, you need to mirror it.

    If that's the case, it's pretty straightforward...here's how I would do it:

    - create your VG on the first 2 disks
    - add the LVs/FSs
    NOTE: in the above, check your options and
    (I would suggest) use "max" for the number
    of PVs the LVs should span for better
    performance and exact mapping (don't have a
    system at hand, so you might want to check
    those 2 options beforehand)
    - once the FSs are created, add the other
    2 disks into the VG (extendvg)
    - then mirror the VG and turn off quorum
    (BTW you could leave quorum on if you had a
    3 disk mirror which could be built, IIRC,
    by adding the 3d set of 2 disks, then
    making copies of the LVs onto that new set)

    All the above can be done via smit(ty) or
    command line.

    Hope that addresses your question.

    Pete

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