Re: BLKTAP

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

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From: Shriram Rajagopalan [mailto:rshriram@cs.ubc.ca] 
Sent: Monday, November 21, 2011 12:03 AM
To: Michael A. Collins
Cc: xen-devel@lists.xensource.com; xen-users@lists.xensource.com
Subject: Re: [Xen-devel] BLKTAP

 

.


drbd/remus - why  do you need blktap ?

shriram

 

>From my readings, I have found only a few examples of using remus.  Most of
them refer to using the following stanza in the disk section of a VM's cfg
file:

tap2:remus:backuphost:anyfreeport|

 

That doesn't work for xl, but even using it with xm causes issues, since
there isn't a tap device without the kernel module.  So I also found out
that drbd uses a tap device to handle the hook in with Xen, so if you want
to have automagic working with block-drbd xen scripts then you have to use
tap.  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, 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 I'm using. 

 

With that being said, I mostly use xl for everything at home, I don't even
have the xend service running, which makes matters worse, since I'm sure
that most of remus uses the xend service and not the API to do the magic.  I
am willing to document my steps and post to the wiki, so that others could
benefit from it!

Mike


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