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eckerc's avatar
eckerc
Level 3
13 years ago

VCS - Mirror based Application Storage

Hello,

I'm planning a evaluation of VCS 6 on RHEL 6.2.

Every Cluster-Application (e.g. apache) should use two SAN Luns from different storage arrays.

When the ressource-group starts, it should build a raid-1 mirror (mdadm), scan/build the lvm, mount the filesystem and start the application.

 

 

Is this possible with VCS?

 

 

Thanks,

Christian

business continuity
Cluster Server
  • mikebounds's avatar
    mikebounds
    13 years ago

    I don't know anything about mdada, but if you are still using Linux LVM (i.e if mdada is at a lower level than LVM or is a tool for LVM rather than replaces LVM - like VxVM replaces LVM), then you should be able to use VCS.  If you need to run any command (like mdada --scan in your case), you can put this in a preonline script if it is the very first command to run in a resource group or if it needs to run at a certain point (like after you import volume group) then you can run it using Application resource where the application resource just creates/monitors ad offlines a lock file for StartProgram,MonitorProgram/StopProgram attributes of Application resource, but also runs custom command as part of StartProgram

    You can use SFHA with ext3, where you use ext3 on a VxVM volume - i.e you only use the VxVM part of SF and don't use vxfs.

    VCS is VERY flexible and if your storgae solution works with other cluster soltuions then it will almost certianly work with VCS.  VCS provides agents like LVM to make life easier, but even if you are using a storage solution that does not use LVM or VxVM, you can use Application agent or write your own agent.

    Mike

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  • mikebounds's avatar
    mikebounds
    Level 6
    13 years ago

    With Veritas Volume Manager (VxVM) which is part of Storage Foundation (SF), you can mirror a volume across SANs and then put this volume under VCS control. Under VCS control you would have a diskgroup resource to import diskgroup, a Mount resource to mount filesystem and an Apache resource to start Apache (you would also have other resouces, notably a IP resource to online a virtual IP).  You would not want to build the mirror and Volme each time you online the service group as "Building" a mirror would mean you would have a empty volume with no data on it.  If you loose a mirror in the volume (because SAN goes down), then the application continues to run on its one copy of data and if the SAN comes back up, then the mirror is rebuilt automatically but this is all part of VxVM, not VCS and the mirror rebuild happens while the resource group is running, not when it is starting.

    So if you have SFHA (SF+VCS) you can do this, but if you just have VCS and plan to use Redhat LVM, then you can still do the same providing LVM can do the same as VxVM and I would think it can and VCS supports Redhat LVM (LVM2) so you would use LVMVolumeGroup resouce type rather than diskgroup.

    Mike

     

     

  • eckerc's avatar
    eckerc
    Level 3
    13 years ago

    Thanks for your fast response.

    We use the mirror-based application storage with other Cluster-Solutions.

    When the service groups goes online, the mirror is built with mdada --scan. This allowes us to resize the lvm group online by adding new mda devices.

    I think SFHA is not a desired solution because I have to use the ext3 filesystem for application data.

     

    Christian

  • mikebounds's avatar
    mikebounds
    Level 6
    13 years ago

    I don't know anything about mdada, but if you are still using Linux LVM (i.e if mdada is at a lower level than LVM or is a tool for LVM rather than replaces LVM - like VxVM replaces LVM), then you should be able to use VCS.  If you need to run any command (like mdada --scan in your case), you can put this in a preonline script if it is the very first command to run in a resource group or if it needs to run at a certain point (like after you import volume group) then you can run it using Application resource where the application resource just creates/monitors ad offlines a lock file for StartProgram,MonitorProgram/StopProgram attributes of Application resource, but also runs custom command as part of StartProgram

    You can use SFHA with ext3, where you use ext3 on a VxVM volume - i.e you only use the VxVM part of SF and don't use vxfs.

    VCS is VERY flexible and if your storgae solution works with other cluster soltuions then it will almost certianly work with VCS.  VCS provides agents like LVM to make life easier, but even if you are using a storage solution that does not use LVM or VxVM, you can use Application agent or write your own agent.

    Mike

  • eckerc's avatar
    eckerc
    Level 3
    13 years ago

    Thanks, this answered my question.

    Sorry what i meant to say was mdadm (the linux software-raid)

    With "scan" and "assemble" you can rebuild and start your sw-raid