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Re: [Xen-devel] BLKTAP



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, Iâm currently running drbd 8.3.11 since
thatâs the version of the kernel module included with Linux 3.1, but
Iâm just using Xenâs phy handler for the disk section of my VMâs
cfg file.

Â

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 Jeremyâs 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
itâs using shared storage and have no need to use it with drbd, but
at home I donât really want to set that up, so I thought drbd would
be a nice start.

Â

Iâve 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 ?
Â

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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