Re: [Xen-users] xl stack problems on CentOS6 XEN4

["Hildebrand, Nils (BIT II 9)" <Nils.Hildebrand@xxxxxxxxxxx>]

Hi Ian,

following the link you provided:
http://lists.xen.org/archives/html/xen-devel/2014-02/msg01190.html

Looks indeed similar to my output
BUT: The following lines are missing on my output:

>> libxl: debug: libxl.c:2605:libxl__device_disk_local_initiate_attach:
>> trying to locally attach PHY device drbd-remus-test with script
>> block-drbd

I can not even see an attempt to call "block-drbd" in my debug-output.

Yes, vmname=xlnur079.

Making drbd primary does not create a device in /dev/ though - hence my 
workaround: cd "/dev/drbd/by-res/" before xl create. That's the place where 
xlnur079 (or at least an symbolic link with that name) resides.

The script (/etc/xen/scripts/block-drbd) I am using is from 
drbd84-utils-8.9.2-1.el6.elrepo.x86_64 - and already seems to contain the "drbd 
or phy" case;
both in the add and the remove branch.

CentOS6 XEN4 is based on the Kernel 3.10.68-11.el6.centos.alt.x86_64 which has 
drbd 8.4.3 built in.
In your mentioned link drbd 9.0 is being handled.

BTW: "remove" seems to be working without problems: xl shutdown will switch the 
drbd-device from primary to secondary (which in my case is bad, since the 
switch on create back onto primary is missing, which makes the reboot of the 
DomU fail).

The question now is (I think): Why is block-drbd not being called on create 
although the xl-parser knows about block-drbd?

So momentarily this looks indeed like a libxl problem.

Time to contact xen-devel, or can we do some deeper digging beforehand?


With kind regards

Nils








-----UrsprÃngliche Nachricht-----
Von: Ian Campbell [mailto:ian.campbell@xxxxxxxxxx] 
Gesendet: Dienstag, 12. Mai 2015 14:55
[...]
> xl create -n shows in the disk-section:  "script": "block-drbd"

That's good/expected.

> So yes - it seems that during (real?) creation the xl-parser does not
> seem to get the right disk-device-type and assumes "phy" instead of
> "drbd".

phy is correct, I think. the drdb: prefix translates into the use of the
block-drdb script which is supposed to make the device available to
dom0.

Xen doesn't provide block-drdb, I think it comes from the drdb project
itself. It's possible that something in libxl is incompatible with that
3rd party script, although I'm sure I've heard rumours of it working
(perhaps not with pygrub?).

http://lists.xen.org/archives/html/xen-devel/2014-02/msg01190.html might
be relevant here.


I take it that "xlnur079" is the "vmname" from:
        disk = [ âdrbd:vmname,xvda,wâ ]
?

It seems that pygrub is being invoked onto xlnur079 directly, whereas I
would have expected the drdb script to have mapped that into some device
or other under /dev/. Perhaps updating the script will make that work
properly?

TBH, I'm struggling to find the code which invokes the script in this
pygrub case. If updating your block-drdb (per that link) doesn't help
then it seems possible you've found a deficiency in the libxl
arrangements here :-( If that turns out to be the case please could you
post that as a bug report to the xen-devel list.
http://wiki.xen.org/wiki/Reporting_Bugs_against_Xen

Thanks,
Ian.

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