Re: performance: domU in disk image or netboot from dom0 ?

[Johan Ihren <johani%johani.org@localhost>]

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Hi,

> I was wondering what was better (regarding performance) between using
> disk images for domU and just "netbooting" them from dom0 ?

I have no hard data on this as I haven't tested it. But both "work  
fine" for a setup with a dozen [not too heavily utilized] VMs on a  
single physical machine.

> My current configuration is:
> - every dom running NetBSD
> - system and pkgsrc in disk images (4Go)
> - data accessed by domUs from dom0 via NFS.
>
> My thinking configuration would be:
> - every doms running NetBSD
> - system, packages and data accessed by domUs from dom0 via NFS/ 
> netboot.
>
> any pros/cons ?
>
> Going further, as every domUs (or at least 99%) will be NetBSD's, what
> about using a single NFS shared system/packages via NFS with a  
> layer for
> conf and temp files.
> Something like:
> domU1:
>         dom0:/exports/domUs     /               nfs
>         dom0:/exports/domU1     /mnt/specific   nfs
>         /mnt/specific           /               union
> domU2:
>         dom0:/exports/domUs     /               nfs
>         dom0:/exports/domU2     /mnt/specific   nfs
>         /mnt/specific           /               union
>
> binary updates are done (once) in dom0:/exports/domUs.
> each vmachine has it's own conf in dom0:/exports/domU*.
> sounds crazy ?

Yes ;-)

I think you'll spend more effort fighting the standard setup than it  
is worth.

I ended up with sharing /usr/share + /usr/X11R6 + /usr/pkg via NFS  
and the rest in machine specific images. That brought down the size  
of the individual images to less than 200MB. But this is because I  
need to be able to install local software on each machine. If that  
isn't needed then you can probably share all of /usr and shrink  
images to ~50MB.

Local config stuff I manage something à la

for vm in $machines ; do
        copy template.img $vm.img
        mount $vm.img somewhere
        rsync $vm specific stuff into somewhere
        umount
done

Johan

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