[DRBD-user] block-drbd and Xen

Florian Haas florian.haas at linbit.com
Tue Sep 2 15:27:54 CEST 2008

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


Alexandre,

As discussed a number of times previously, the drbd:resource method only
works if you are _not_ using pygrub or domUloader.py, as those two make
assumptions about VBD's that are limited to supporting regular files and
block devices already available in /dev. If you _are_ using pygrub, or
domUloader.py, or (probably) anything else that is invoked via the
"bootloader" option, the drbd:resource syntax is not for you.

So if you want to use live migration in conjunction with DRBD-backed
Xen, you can
- use "kernel", "ramdisk" and "extra" options, and drbd:resource in your
"disk" section (this means you wouldn't be using any of said
pseudo-bootloaders), or
- use a bootloader such as pygrub and domUloader.py, and refer to your
VBD as phy:/dev/drbdXX, or
- use a bootloader such as pygrub and domUloader.py, and refer to your
VBD as phy:/dev/vg/lv, while using CLVM on top of DRBD. or
- use a bootloader such as pygrub and domUloader.py, and use a file:
VBD, where that file is located on GFS o OCFS2 on top of DRBD.

All of these require dual-Primary mode, and it is up to you to make sure
your two cluster nodes don't start the affected Xen domU twice and thus
produce conflicting writes on said device. The drbd:resource syntax, and
the associated Xen block script, only is designed to make that easier
for you.

>> On 9/1/08, Jerry Amundson <jamundso at gmail.com> wrote:
>> Doesn't matter. Most people seem to find the *official* answer, which
>>  *official* people refuse to change, yet many times just does not work.

Jerry, the documentation sources are at
http://git.drbd.org/?p=drbd-documentation.git. Since I apparently fail
to understand just what you find unclear about said portion of the
documentation, I would much appreciate a patch. It would help way more
than recurrently complaining about allegedly having your time wasted. An
extended README for documentation contributors is at
http://git.drbd.org/?p=drbd-documentation.git;a=blob;f=README. Thanks.

Florian

-- 
: Florian G. Haas
: LINBIT Information Technologies GmbH
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