[Engine-devel] Proposal for support ISO domain on other types of file based storage.

[Mark Wu]

On 03/18/2013 04:43 PM, Ayal Baron wrote:
>
> ----- Original Message -----
>> Mark Wu :
>>> On Sun 17 Mar 2013 10:12:55 PM CST, Ayal Baron wrote:
>>>>
>>>> ----- Original Message -----
>>>>> Hi guys,
>>>>>
>>>>> Currently, ISO domain is only supported on NFS storage. It could
>>>>> improve the ease of use if it allows other types
>>>>> of file based storage to store ISO images. After an
>>>>> investigation, I
>>>>> found there's not any restriction on this idea.
>>>>> So the whole work is removing the limitation on engine side. That
>>>>> means engine should allow ISO domain could
>>>>> have different storage type from the data center it's attached,
>>>>> like
>>>>> what we do with nfs ISO domain in SAN DC.
>>>>>
>>>>> I start this idea with localfs. I know local storage can't be
>>>>> seen in
>>>>> cluster level. But it also provides a choice if no
>>>>> NFS available. VMs can be created on the host which has the ISO
>>>>> repo,
>>>>> and then be migrated to any other host in the cluster.
>>>>> I have done the initial patches: allow creation ISO domain on
>>>>> localfs
>>>>> [1] and support import ISO domain on localfs [2]
>>>>> I don't have much experience in java/j2ee/web development and
>>>>> engine
>>>>> architecture. The patches just work for me.
>>>>> I am not sure if it will bring some potential problems. So any
>>>>> feedback on the patch or the idea will be appreciated very much.
>>>> Haven't looked at the patches yet, but wrt the idea, I agree on
>>>> the
>>>> need (being able to attach ISOs from anywhere and not just nfs)
>>>> but I
>>>> think the way to do this should be by getting rid of the ISO
>>>> domain
>>>> type altogether.
>>> I think ISO domain on localfs is useful for a simple setup or demo,
>>> such as oVirt all-in-one.
>>>
>>>> Basically what we need is:
>>>> 1. a way to connect to file based storage (let's leave block aside
>>>> for now) - this already exists via the connectStorageServer verb
>>>> 2. a way to list and present a file system tree in gui (give an
>>>> arbitrary path to vdsm and list content) and possibly filter
>>>> results
>>>> by type (vfd, iso) - does not exist today. Possibly some security
>>>> aspects here that need hashing out.
>>>> 3. a way to specify a path to a file when attaching an iso/vfd to
>>>> a
>>>> VM - this is the way it works today
>>>>
>>>> This would devoid the need for isoUploader and allow users to
>>>> simply
>>>> manage an nfs export with files.
>>>> Next step would be to make connectStorageServer support httpfs [1]
>>>> and then we'd be able to mount ISOs directly over http (hopefully
>>>> this would be sufficient to support ISOs stored on S3, swift,
>>>> glance,
>>>> etc).
>>> Actually, we could use the qemu curl backend image support
>>> directly.
>>> That means we don't need mount the place storing ISO images. We can
>>> just maintain a list of ISO image with its link, which could be
>>> http,
>>> ftp and ssh.
>> That will be fine to start a VM on a existing extern ISO image. I
>> also
>> would like to maintain a ISO image cache on the local host to avoid
>> to
>> re-streaming the ISO image from the ISO image repositories every
>> time.
>> That will be helpful for people who is suffered from the network
>> bottleneck.
> We have a similar requirement for glance support (not limited to ISOs, rather to all read-only images) so that should be tackled with a broader solution.
In that case,  I suppose qemu's copy-on-read + httpfs (you mentioned 
above) could help.  It can avoid accessing the same backing file sectors 
repeatedly.
But the copied content can't be shared by multiple VM using the same 
backend image.

>
>>>> [1] http://httpfs.sourceforge.net/
>>>>
>>>>>
>>>>> Mark.
>>>>>
>>>>> [1] http://gerrit.ovirt.org/#/c/12687/
>>>>> [2] http://gerrit.ovirt.org/#/c/12916/
>>>>>
>>>>> _______________________________________________
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>>>>> Engine-devel at ovirt.org
>>>>> http://lists.ovirt.org/mailman/listinfo/engine-devel
>>>>>
>>>
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>>>
>>
>> --
>> ---
>> 舒明 Shu Ming
>> Open Virtualization Engineerning; CSTL, IBM Corp.
>> Tel: 86-10-82451626  Tieline: 9051626 E-mail: shuming at cn.ibm.com or
>> shuming at linux.vnet.ibm.com
>> Address: 3/F Ring Building, ZhongGuanCun Software Park, Haidian
>> District, Beijing 100193, PRC
>>
>>
>>

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