Re: BLKTAP

["Michael A. Collins" <mike.a.collins@ark-net.org>]

On 22.11.2011 01:56, Shriram Rajagopalan wrote:

> eh? I dont think so. with drbd based backend for xen VMs (with or 
> without remus),
> you just use the drbd:<resourceName> syntax (much like phy:...).
> And then the block-drbd script in /etc/xen/scripts/ takes care of the 
> rest of the magic.
> There is no tapdisk involved in this procedure.

> In essence, the block-drbd script just
> 1. parses the drbd:<resourceName> syntax to determine which one of
>  the /dev/drbd[X] devices belong to the <resourceName>,
> 2. does some sanity checks
> 3. promotes <resourceName> in the host to "Primary" and then

> the rest of the control flow happens akin to a phy device, with 
> /dev/drbd[X] being
> supplied as the path to the disk backend.
>
> You could do this manually too in two simple steps.
>  1. On the host where you want to launch the VM, promote the drbd 
> disk to Primary
>  (ensure that the other end is in secondary state)
>  2. change the VM's disk config to 
> phy:/dev/drbd/by-res/<resourceName>
>  and you are good to go.
>  [Though with remus, you ll have to hack the 
> tools/python/xen/remus/device.py script to
>  recognize the /dev/drbd/* URI.]>

The drbd:<resource> syntax works for xm, but not for xl.  I'll have to 
work on that.  Below is what xl spits out trying to create the domain.

dc.xl: config parsing error in disk specification: unknown value for 
format: near `xvda' in `drbd:dc,xvda,w'

> With all that said and done, I’m currently running drbd 8.3.11 since
> that’s the version of the kernel module included with Linux 3.1, but
> I’m just using Xen’s phy handler for the disk section of my VM’s
> cfg file.
>
>  
>
> I see that there is a nice howto for debian on remusha.wikidot.com
> [5], but again it uses a 2.6.32 kernel from Jeremy’s git repo, which
> has the tap kernel module.  I again assert that currently there is
> very little out there that would help to get someone started using
> remus with drbd in the linux 3.1.x world.  I run remus at work, but
> it’s using shared storage and have no need to use it with drbd, but
> at home I don’t really want to set that up, so I thought drbd would
> be a nice start.
>
>  
>
> I’ve started diffing the 8.3.9 branch of drbd with your changes for
> remus and will see how hard it is to get that in the 8.3.11 version
>
>>
>> Is the remusified drbd (8.3.9) not compiling under the 3.1.x kernel
>> anymore or are you interested in
>> the latest version of DRBD + the remus stuff ?
>>  
>>
>> shriram

I am interested in running the latest drbd changes with remus.  But I 
am interested in getting this to work through the xl interface more than 
anything.



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