[one-users] Setting the "SHAREABLE" attribute

[Javier Fontan]

I've been digging a bit more in the shareable issue and it seems that
setting "shareable" to a disk just disables cache in qemu/kvm[1]:

--8<------
4158         virBufferAsprintf(&opt, ",cache=%s", mode);
4159     } else if (disk->shared && !disk->readonly) {
4160         virBufferAddLit(&opt, ",cache=off");
4161     }
------>8--

Isn't it enough to disable cache for disks that can be migrated?

[1] http://libvirt.org/git/?p=libvirt.git;a=blob;f=src/qemu/qemu_command.c;h=e1ff2872209de43a5d9591d7096ca887ed429df3;hb=HEAD#l4159

On Tue, Nov 19, 2013 at 1:16 PM, Gareth Bult <gareth at linux.co.uk> wrote:
> Hi,
>
> I've bypassed this for now by adding a line to "deploy" that says;
> /var/lib/one/remotes/hooks/vdc/deploy.py $domain
> #(just below cat > $domain)
>
> And adding the python script;
>
> #!/usr/bin/python
>
> import xml.etree.ElementTree as ET
> from sys import argv
> original = ET.parse(argv[1])
> params = original.findall(".//disk")
> for p in params: if p.get('device') == 'disk':
> p.insert(0,ET.Element("shareable",{}))
> original.write(argv[1])
>
> This makes all devices of type "disk" shareable.
>
> I *think* anyone using current versions of KVM/libvirt who want to do live
> migration will need this ... unless
> they set "cache=none", which doesn't always do great things for your
> performance ...
>
>
> --
> Gareth Bult
> "The odds of hitting your target go up dramatically when you aim at it."
>
>
>
> ________________________________
> From: "Javier Fontan" <jfontan at opennebula.org>
> To: "Gareth Bult" <gareth at linux.co.uk>
> Cc: users at lists.opennebula.org
> Sent: Tuesday, 19 November, 2013 11:54:07 AM
> Subject: Re: [one-users] Setting the "SHAREABLE" attribute
>
>
> Right now there is no way to set this value as the deployment file (libvirt
> xml file) is generated in the core and lacks this functionality.
>
> We are evaluating the best way to fix. Adding a "raw" parameter for DISKS
> will be enough or would it be better to have also a default RAW section for
> all the disks?
>
> There are more generic and maybe better ways to add this feature but we are
> really near to the 4.4 release and we are not sure if they can make the
> feature cut.
>
> Cheers
>
>
> On Mon, Nov 18, 2013 at 11:57 AM, Gareth Bult <gareth at linux.co.uk> wrote:
>>
>> Hi,
>>
>> For the most recent versions of libvirt, in order to do a live migration
>> with writethru cache turned
>> on, the "<SHAREABLE/>" attribute needs to be set in the DISK section of
>> the configuration. "virt-manager"
>> has a tick box for this in it's disk setup section .. is there an easy way
>> to implement this in OpenNebula?
>>
>> tia
>>
>> --
>> Gareth Bult
>> "The odds of hitting your target go up dramatically when you aim at it."
>>
>>
>>
>>
>> _______________________________________________
>> Users mailing list
>> Users at lists.opennebula.org
>> http://lists.opennebula.org/listinfo.cgi/users-opennebula.org
>>
>
>
>
> --
> Javier Fontán Muiños
> Developer
> OpenNebula - The Open Source Toolkit for Data Center Virtualization
> www.OpenNebula.org | @OpenNebula | github.com/jfontan
>



-- 
Javier Fontán Muiños
Developer
OpenNebula - The Open Source Toolkit for Data Center Virtualization
www.OpenNebula.org | @OpenNebula | github.com/jfontan