[Gllug] Xen - bit of a ramble

[Matthew Cooke]

>
>Hi,
>
>Thanks for your informed reply.  Can xen also allocate
>shares of the CPU (and for that matter other system
>resources) out to the virtual machines so that one
>bad process in one bad VM does not eat up all the CPU.
>Of putting this another way in Solaris terms can xen
>perform "Fair shares" scheduling?

I don't know how "fair scheduling" works on solaris, but yes you get a share 
of the CPU or to be more accurate you get a guaranteed minimum CPU time.

So on one machine my Xen Vm is roughly 1/8th of the machine. This guarantees 
me 1/8th of the CPU time (minus a small overhead). Most of the time I 
actually get nearer 100% of the CPU time since the other vms aren't heavily 
loaded but I am "roughly" guarantees to get at least my 1/8th. It's the 
ability to effectively use other VMs unused CPU cycles that makes a hosted 
Xen solution quite cost efficient.

Memory allocation is partitioned differently, you get a physical fixed 
amount of ram. This is real ram unlike some other virtualisation solutions 
which allow you to share ram a make it appear all VM's have more memory than 
is actually available.


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