Re: [opensuse] Re: Xen on production environments

On Sun, 2008-03-16 at 13:01 -0400, Ciro Iriarte wrote:
2008/3/13, Hans Witvliet <hwit@xxxxxxxxxxx>:

Hi Ciro,

We have a dozen dl360 dl380, each of them two dual core xeons and
between 6 or 8 GB ram, and one dual quad core with 24 GB ram.
All of them are equipped with a fibre channel card towards a IBM-SAN.

Sounds nice :D


Most of them run 10.3, one of them Ubuntu-geisty.

I think we'll go with SLES10

I tried to rebuild the dom-u's with 32-bit-pae.
I thought that was a wise move, as most of the clients have between
512MB and 2048MB mem, so 64-bit architecture seems to be a waste.

Problem however is that live migration of pae-images leads to disaster.
Dom-u freezes, and dom-0 has to be hard rebooted. identical images made
with 64bit cause no problem what so ever.

I've read that all the VM's and VM hosts need to run the same
architecture for the LM to work.


performance is never an issue.
Like one other poster mentions, sometimes the clock stands still, which
causes "funny situations".

We use NTP for all our servers, does the problem apply to lower to
that level? (won't use it for the DomUs..)


We used to have all services in seperate dom-u's, which normally work
well. But after a power blackout we found out that we created a
rat-race. Dom-0 needed an dhcp-address, but the dhcpd-server was another
dom-u, Same problem with both master & slave ldap server in an dom-u, or
master & slave DNS-server....

Can the VMs be automatically started?

Most of the dom-u's are LAMP-machines or dedicated applications that
have to run for some months.

So be carefull about race-conditions..

Luckily we won't use the VMs for infrastructure machines...


Besides that, it works like a charm.

Good to know!



Hans


Some quick replies...

Whats the benefit of sles in this respect ?
(Open gets more frequent updates)

About 32-clients on 64-hosts, You can create, stop and start them.
Which is nice if you have a lot of 32-bit and 64- bit machines.
It means you can start any image on any host.
Only live migrations fails....

NTP: All of our systems gets the same config, including ntp-source.
We use a library of xml-files to create them. No manual intervention
needed. It's a known bug at a lower level.

About starting, yes you can config to start virtual machines
automatically.
Point however was (in my case) if you slowly migrate all kinds of
functionalities, all remains working well.
After a sudden blackout however:
In my dhcpd-server-image, no addresses are defined, but dns-names.
And the dns-server coukd not be started, because that image could not
perform an dhcp-request. Could not login on any dom-0, because
authentications was done towards an ldap-machine, which could not be
started, because it couldn't get an ip-address. Besides, the hostname
"ldap" could not be resolved, because the dns-server could not be
started...
The original idea behind it was to get a fail-save configuration with
LVS virtual servers and heart-beat. Works wel if only ony thing goes
down, not if all goes down.

So now some machines have fixed addresses, and some services run on bare
metal, instead of virtual machines....

Only thing that realy surprised me is that instead of all the warnings
we've got a number of asterisk-voip-servers in an xen images running
without any speech quality degredation (both 1.4 and 1.6 versions)

hw
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