[Users] what is "distributed image repository"

[Itamar Heim]

On 02/27/2013 12:51 PM, bigclouds wrote:
>
> thanks,i know a little more. but i do not understand fully.  distrubute
> filesystem  is more understandable.
> specially,,for SAN(iscsi,fc)  it is hard to share luns between nodes(not
> reliable), even use LVM,CLVM.
>
> would you explain it ( SAN case)?and it is hard to connect
> 'local directory' with distrbuted repo.

true.
even a single LUN, turned into a VG with LVM, can be used by all nodes 
in the cluster.
an LV is created for each disk element (part of a chain in the disk 
construct).
it's "like CLVM", only using only a single node (the "SPM") to do the 
meta data changes (lvcreate) and other hosts to only consume the LV's 
for running VMs.
this allows to scale to clusters of 50, 100 or more nodes.

HTH,
    Itamar


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> At 2013-02-27 17:55:45,"Gianluca Cecchi" <gianluca.cecchi at gmail.co
>   m> wrote:
>>On Wed, Feb 27, 2013 at 10:44 AM, bigclouds  wrote:
>>> there is a sentense 'Implements a distributed image repository over the
>>> supported storage types (local directory, FCP, FCoE, iSCSI, NFS, SAS)
>>> '  on http://www.ovirt.org/Architecture.
>>>
>>> what is "distributed image repository"?
>>>
>>> thanks.
>>
>>Example
>>I have a test environment where a Host is connected to several FCP LUNs.
>>Each LUN becomes a storage domain for this host and the other hosts in
>>the same cluster.
>>So I have many VMs whose images resides on different storage domains
>>(and so different LUNs).
>>I can move a disk of a VM from a storage domain to another one.
>>I think you can also have a mixed situation where a two disks' VM has
>>one disk on a storage domain and the other one in another.
>>
>>So I think it is to be explained this way the  "distributed image repository".
>>
>>And also "distributed" in the sense of different storage domain types,
>>even if I think at this time one DC cannot have a mix of different
>>storage domain types...
>>
>>Gianluca
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