On Thu, Dec 4, 2014 at 12:54 PM, mad Engineer <themadengin33r@gmail.com> wrote:
sorry i am wrong its the data domain that stores virtual disk images,I
have no idea how ovirt shares block device across hosts.Looks like i
need to try that for understanding how its implemented.In case of
vmware they uses vmfs file system for sharing block device among
hosts.I currently have no issues with my NFS shared storage so dont
have any plan to use iscsi,but just curious how the implementation
is.In my existing non ovirt environment,SAN block devices is exported
and its shared using GFS.Is ovirt using any simillar method to achieve
shared block device.


oVirt uses a different approach altogether (this is why it can scale to clusters with hundreds of hosts, unlike vmware). The idea is pretty simple
1. format the shared block storage with LVM
2. Every VM disk image is an LV
3. manage host access to separate LVs using simple lvchange.

Of course there's much more to the way this is implemented, but very simply -  no two hosts have write access to the same LV, unless it is specified as a shared disk, so no clustered FS is needed, no scsi reservations are needed and this concept scales, unlike vmfs, gfs, and other such systems.


 


On Thu, Dec 4, 2014 at 9:10 PM, mad Engineer <themadengin33r@gmail.com> wrote:
> Thanks Gianluca,it says only NFS is supported as export domain.I
> believe export domain is the one i am currently using for live
> migrating vms across hosts.So iscsi is not supported,please correct me
> if i am wrong.Thanks for your help
>
> On Thu, Dec 4, 2014 at 9:00 PM, Gianluca Cecchi
> <gianluca.cecchi@gmail.com> wrote:
>> On Thu, Dec 4, 2014 at 4:23 PM, mad Engineer <themadengin33r@gmail.com>
>> wrote:
>>>
>>> Thanks Maor,in non ovirt kvm setup i use GFS2 to make the block device
>>> shareable across multiple hosts.Could you tell me how is it achieved
>>> in ovirt.
>>>
>>> Regards
>>>
>>
>> First step the admin guide:
>> http://www.ovirt.org/OVirt_Administration_Guide
>>
>> and in particular the Storage chapter and the related iSCSI part:
>> http://www.ovirt.org/OVirt_Administration_Guide#.E2.81.A0Storage
>>
>> Also, for multipath in case you need it:
>> http://www.ovirt.org/Feature/iSCSI-Multipath
>>
>> HIH,
>> Gianluca
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