LPAR virtual scsi - all disks on same adapter? - Aix

This is a discussion on LPAR virtual scsi - all disks on same adapter? - Aix ; I'm fresh back from LPAR class, and am setting up my first partitioned system. I have my vio server up and am starting to set up virtual disks for my partitions to use. I plan on using logical volumes, so ...

+ Reply to Thread
Results 1 to 4 of 4

Thread: LPAR virtual scsi - all disks on same adapter?

  1. LPAR virtual scsi - all disks on same adapter?

    I'm fresh back from LPAR class, and am setting up my first partitioned
    system. I have my vio server up and am starting to set up virtual
    disks for my partitions to use. I plan on using logical volumes, so I
    can carve my 73GB drives into smaller disks for my partitions to boot
    from. In doing this, I ran across a bit in my class manual that says:

    "If a logical volume is exported as a virtual device, all physical
    volumes that make up the volume group in which the logical volume is
    contained must be attached to the same adapter".

    Now, I can do this (just barely - these adapters only have 3 disk
    slots each!), but I wonder why. I had planned on using LVM mirroring
    for these logical volumes, but putting them on a single adapter
    introduces a single point of failure.

    Can anyone explain why this limitation exists, and if it has perhaps
    been lifted in some more recent release of the vioserver or the
    hypervisor? I'm running vioserver version 1.4.1, and my host system
    is a 561 at firmware level 322 (which just came out a few weeks ago).
    I plan on running AIX 5.3 06 01 in my partitions.


  2. Re: LPAR virtual scsi - all disks on same adapter?

    rodak wrote:
    > I'm fresh back from LPAR class, and am setting up my first partitioned
    > system. I have my vio server up and am starting to set up virtual
    > disks for my partitions to use. I plan on using logical volumes, so I
    > can carve my 73GB drives into smaller disks for my partitions to boot
    > from. In doing this, I ran across a bit in my class manual that says:


    > "If a logical volume is exported as a virtual device, all physical
    > volumes that make up the volume group in which the logical volume is
    > contained must be attached to the same adapter".


    > Now, I can do this (just barely - these adapters only have 3 disk
    > slots each!), but I wonder why. I had planned on using LVM mirroring
    > for these logical volumes, but putting them on a single adapter
    > introduces a single point of failure.


    > Can anyone explain why this limitation exists, and if it has perhaps
    > been lifted in some more recent release of the vioserver or the
    > hypervisor? I'm running vioserver version 1.4.1, and my host system
    > is a 561 at firmware level 322 (which just came out a few weeks ago).
    > I plan on running AIX 5.3 06 01 in my partitions.


    The way it was explained to me is that VIO client writes do not go
    through the LVM layer on the VIO server. Furthermore, as I understand it,
    the entire client LV needs to be contained on a single PV on the VIO server.
    If you are looking to avoid a single point of failure, create a second VIO
    server, allocate another LV from it to the client and use LVM mirroring at
    the client level.

    Regards,
    Gregory Young


  3. Re: LPAR virtual scsi - all disks on same adapter?

    On Oct 16, 7:56 pm, Gregory Young wrote:
    > rodak wrote:
    > > I'm fresh back from LPAR class, and am setting up my first partitioned
    > > system. I have my vio server up and am starting to set up virtual
    > > disks for my partitions to use. I plan on using logical volumes, so I
    > > can carve my 73GB drives into smaller disks for my partitions to boot
    > > from. In doing this, I ran across a bit in my class manual that says:
    > > "If a logical volume is exported as a virtual device, all physical
    > > volumes that make up the volume group in which the logical volume is
    > > contained must be attached to the same adapter".
    > > Now, I can do this (just barely - these adapters only have 3 disk
    > > slots each!), but I wonder why. I had planned on using LVM mirroring
    > > for these logical volumes, but putting them on a single adapter
    > > introduces a single point of failure.
    > > Can anyone explain why this limitation exists, and if it has perhaps
    > > been lifted in some more recent release of the vioserver or the
    > > hypervisor? I'm running vioserver version 1.4.1, and my host system
    > > is a 561 at firmware level 322 (which just came out a few weeks ago).
    > > I plan on running AIX 5.3 06 01 in my partitions.

    >
    > The way it was explained to me is that VIO client writes do not go
    > through the LVM layer on the VIO server. Furthermore, as I understand it,
    > the entire client LV needs to be contained on a single PV on the VIO server.
    > If you are looking to avoid a single point of failure, create a second VIO
    > server, allocate another LV from it to the client and use LVM mirroring at
    > the client level.
    >
    > Regards,
    > Gregory Young


    Thanks, Gregory. Yes, you're right, two VIO servers does make a lot
    more sense. I was considering that anyway. About the LV being
    contained within a single PV - do you have any reference where I can
    verify that? If it's a limitation that has perhaps been removed with
    more recent software, I'd like to know, since I may have the need to
    create a virtual LV that's larger than a single PV, and it would be
    simpler to create it as a single LV.


  4. Re: LPAR virtual scsi - all disks on same adapter?

    On Oct 17, 9:33 am, rodak wrote:
    > On Oct 16, 7:56 pm, Gregory Young wrote:
    >
    >
    >
    > > rodak wrote:
    > > > I'm fresh back from LPAR class, and am setting up my first partitioned
    > > > system. I have my vio server up and am starting to set up virtual
    > > > disks for my partitions to use. I plan on using logical volumes, so I
    > > > can carve my 73GB drives into smaller disks for my partitions to boot
    > > > from. In doing this, I ran across a bit in my class manual that says:
    > > > "If a logical volume is exported as a virtual device, all physical
    > > > volumes that make up the volume group in which the logical volume is
    > > > contained must be attached to the same adapter".
    > > > Now, I can do this (just barely - these adapters only have 3 disk
    > > > slots each!), but I wonder why. I had planned on using LVM mirroring
    > > > for these logical volumes, but putting them on a single adapter
    > > > introduces a single point of failure.
    > > > Can anyone explain why this limitation exists, and if it has perhaps
    > > > been lifted in some more recent release of the vioserver or the
    > > > hypervisor? I'm running vioserver version 1.4.1, and my host system
    > > > is a 561 at firmware level 322 (which just came out a few weeks ago).
    > > > I plan on running AIX 5.3 06 01 in my partitions.

    >
    > > The way it was explained to me is that VIO client writes do not go
    > > through the LVM layer on the VIO server. Furthermore, as I understand it,
    > > the entire client LV needs to be contained on a single PV on the VIO server.
    > > If you are looking to avoid a single point of failure, create a second VIO
    > > server, allocate another LV from it to the client and use LVM mirroring at
    > > the client level.

    >
    > > Regards,
    > > Gregory Young

    >
    > Thanks, Gregory. Yes, you're right, two VIO servers does make a lot
    > more sense. I was considering that anyway. About the LV being
    > contained within a single PV - do you have any reference where I can
    > verify that? If it's a limitation that has perhaps been removed with
    > more recent software, I'd like to know, since I may have the need to
    > create a virtual LV that's larger than a single PV, and it would be
    > simpler to create it as a single LV.


    No it's per design, you are stuck with that limitation. The reason is
    this:
    - on a VIO you create a VG with disks from different adapters
    - you move an adapter from one LPAR to the other
    - you just broke your VG

    So to avoid this, they limit us! Solution: 2 VIO, one adapter each,
    mirror on client.

    Nic


+ Reply to Thread