[Pacemaker] starting a xen-domU depending on available hardware-resources using SysInfo-RA

[Dejan Muhamedagic]

Hi,

On Tue, Sep 28, 2010 at 11:00:18AM +0200, Sascha Reimann wrote:
> howdy!
> 
> I'm trying to configure a resource (xen-domU) that could start on 2
> nodes (preferred on node server01):
> 
> primitive v01 ocf:heartbeat:Xen \
> 	params xmfile="/etc/xen/conf.d/v01.cfg" allow-migrate="true"
> location loc-v01p v01 200: server01
> location loc-v01s v01 100: server02
> 
> That's working fine so far, but I want to ensure that there's enough
> hardwareresources available on server01, so I've set up a modified
> SysInfo-RA to put the ram_total and ram_free values of xen (xm
> info|awk '/free_memory/ {print $3}') to the statusinformation of the
> CIB:
> 
> server01:~$ cibadmin -Q -o status|grep status-server01-ram
> <nvpair id="status-server01-ram_total" name="ram_total" value="8191"/>
> <nvpair id="status-server01-ram_free" name="ram_free" value="2000"/>
> 
> This is working fine, too. BUT:
> 
> When I create a rule like the one below, the xen-domU keeps
> restarting (or moving to server02 where the same happens), which is
> correct since the SysInfo-RA updates the statusinformation to
> value="0" after a start and back to value="2000" after a stop in
> this example.
> 
> location loc-resv01 v01 \
> 	rule $id="loc-resv01-rule" -inf: ram_free lt 2000

An interesting issue :-)

Well, you can introduce resource stickiness and use that to
outweigh the negative score coming from the lack of memory (use
something less than inf). You may also consider using the amount
of free memory as a score.

HTH,

Dejan

> Can anybody help?
> 
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