Direct luns are disks that are not managed by oVirt. Ovirt communicates
directly with the lun itself, without any other layer in between (like lvm
in image disks).
The advantage of the direct lun is that it should have better performance
since there's no overhead of another layer in the middle.
The disadvantage is that you can't take a snapshot of it (when attached to
a vm, of course), can't make it a part of a template, export it, and in
general - you don't manage it.


Regards,
Idan

On Mon, Jun 12, 2017 at 10:10 PM, Stefano Bovina <bov...@gmail.com> wrote:

> Thank you very much.
> What about "direct lun" usage and database example?
>
>
> 2017-06-08 16:40 GMT+02:00 Elad Ben Aharon <ebena...@redhat.com>:
>
>> Hi,
>> Answer inline
>>
>> On Thu, Jun 8, 2017 at 1:07 PM, Stefano Bovina <bov...@gmail.com> wrote:
>>
>>> Hi,
>>> does a storage best practise document for oVirt exist?
>>>
>>>
>>> Some examples:
>>>
>>> oVirt allows to extend an existing storage domain: Is it better to keep
>>> a 1:1 relation between LUN and oVirt storage domain?
>>>
>> What do you mean by 1:1 relation? Between storage domain and the number
>> of LUNs the domain reside on?
>>
>>> If not, is it better to avoid adding LUNs to an already existing storage
>>> domain?
>>>
>> No problems with storage domain extension.
>>
>>>
>>> Following the previous questions:
>>>
>>> Is it better to have 1 Big oVirt storage domain or many small oVirt
>>> storage domains?
>>>
>> Depends on your needs, be aware to the following:
>> - Each domain has its own metadata which allocates ~5GB of the domain
>> size.
>> - Each domain is being constatntly monitored by the system, so large
>> number of domain can decrease the system performance.
>> There are also downsides with having big domains, like less flexability
>>
>>> There is a max num VM/disks for storage domain?
>>>
>>>
>>> In which case is it better to use "direct attached lun" with respect to
>>> an image on an oVirt storage domain?
>>>
>>
>>>
>>
>>> Example:
>>>
>>> Simple web server:   ----> image
>>> Large database (simple example):
>>>    - root,swap etc: 30GB  ----> image?
>>>    - data disk: 500GB    -----> (direct or image?)
>>>
>>> Regards,
>>>
>>> Stefano
>>>
>>> _______________________________________________
>>> Users mailing list
>>> Users@ovirt.org
>>> http://lists.ovirt.org/mailman/listinfo/users
>>>
>>>
>>
>
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> Users@ovirt.org
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>
>
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