----- "Dennis J." dennisml@conversis.de wrote:
Hi, I'm wondering about the impact of using both dom0 and domU's on a server at the same time. I'm worried about the performance impact of running a Mysql server in a domU and now I'm thinking about moving the Mysql part of a LAMP setup into dom0 and running a few Apache guests as domUs. Since the Apaches will serve mostly from an NFS share they won't have much impact on the disk i/o so the database should be able to utilize the local storage without much interference from the guests. The plan is to limit dom0 to let's say 4gb of ram and then use the rest of it for the VMs.
Has anyone experinece with this kind of "mixed" setup (physical/virtual). Are there any known problems with this approach?
Running processes in dom0 that aren't for running Xen is going to destroy your domU I/O performance. The backends are just processes. If you take time away from those processes for other things, performance will suffer. You should run some load tests and see if it suits your model, though.
Running the MySQL process in dom0 isn't going to get you very much of a performance boost if your MySQL configuration is tuned properly, either.
With this in mind, that dom0 should be lightweight, is there a list of optimal minimal services to run in a CentOS dom0?
I assume no need to uninstall, just a service toggle off in runlevels 3 and 5?
I believe some apps and services might be useful if a maintenance task required some utils running out of dom0 with some burden on the domUs for a while.
Regards, Ben
Running processes in dom0 that aren't for running Xen is going to destroy your domU I/O performance. The backends are just processes. If you take time away from those processes for other things, performance will suffer. You should run some load tests and see if it suits your model, though.
Running the MySQL process in dom0 isn't going to get you very much of a performance boost if your MySQL configuration is tuned properly, either.
++ 04/02/09 09:27 -0500 - Ben Montanelli:
With this in mind, that dom0 should be lightweight, is there a list of optimal minimal services to run in a CentOS dom0?
I assume no need to uninstall, just a service toggle off in runlevels 3 and 5?
I run this in Centos 5.x domU's:
for svc in acpid apmd bluetooth cpuspeed gpm microcode_ctl \ pcscd smartd irqbalance mdmonitor; \ do chkconfig $svc off; \ service $svc stop; \ done
And in addition to that I also run this in Centos 5.x dom0's:
for svc in bluetooth gpm pcscd cups avahi-daemon yum-updatesd; \ do chkconfig $svc off; \ service $svc stop; \ done
There is some overlap, and possibly services that I've missed - but these are from my notes when I had a look at it. Feel free to comment.
Cheers, Henrik
++ 04/02/09 16:56 +0100 - Henrik Holmboe:
[...]
And in addition to that I also run this in Centos 5.x dom0's:
for svc in bluetooth gpm pcscd cups avahi-daemon yum-updatesd; \ do chkconfig $svc off; \ service $svc stop; \ done
Oh, I forgot this for dom0's:
for svc in nfslock portmap rpcidmapd cups yum-updatesd; \ do chkconfig $svc off; \ service $svc stop; \ done
Thank you Henric, exactly what I was looking for. I hope to try this tweek over the weekend.
I guess many of us want the optimized "grail" dom0. (Please forgive me if this is in the archive, I find nothing to little on this topic.)
Does this look like a decent summary of your suggestions:
-bluetooth
-gpm
-pcscd
-cups
-avahi-daemon
-yum-updatesd (oh yeah)
-nfslock
-portmap (hmnn, not needed on new domUs, NIC configs as well as migration for xend? Truly do not know the answer here.)
-rpcidmapd
I'm only slightly above noob on Xen and I still like to do a bit in gui, (fluxbox or Gnome/XFCE4), so I can see right away if there are any balks in the service window. I do know that dropping windows manager(s) opens up some resources, but I still need the assist.
I'm weak in dom0 configuration and securing. I am relying on a separate NIC (private IP, tight ingress/egress) for dom0 with profound hardware firewalling and monitoring until I get this aspect comfortably nailed down. I just don't trust my knowledge of inherent linux firewalling for servers yet.
I doubt I will ever drop the separate NIC and firewall setup on dom0 though.
Henrik Holmboe wrote:
++ 04/02/09 16:56 +0100 - Henrik Holmboe:
[...]
And in addition to that I also run this in Centos 5.x dom0's:
for svc in bluetooth gpm pcscd cups avahi-daemon yum-updatesd; \ do chkconfig $svc off; \ service $svc stop; \ done
Oh, I forgot this for dom0's:
for svc in nfslock portmap rpcidmapd cups yum-updatesd; \ do chkconfig $svc off; \ service $svc stop; \ done
Ben Montanelli wrote on Wed, 04 Feb 2009 11:50:04 -0500:
I guess many of us want the optimized "grail" dom0.
There is none. It depends on your needs.
Kai
Henrik Holmboe wrote on Wed, 4 Feb 2009 16:58:50 +0100:
for svc in nfslock portmap rpcidmapd cups yum-updatesd; \
Or you just don't install this stuff beforehand ;-)
Kai
++ 04/02/09 18:31 +0100 - Kai Schaetzl:
Henrik Holmboe wrote on Wed, 4 Feb 2009 16:58:50 +0100:
for svc in nfslock portmap rpcidmapd cups yum-updatesd; \
Or you just don't install this stuff beforehand ;-)
Yes, that's true. However these are all in the "Virtualization" groupinstall by default. You could of course uninstall alot of software, instead of just disabling them as with my example.
h.
-
Ben Montanelli -
Christopher G. Stach II -
Henrik Holmboe -
Kai Schaetzl