Re: [Xen-devel] Questions about certain Xen limits and features

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 7/11/08 14:01, "Vessey, Bruce A" <Bruce.Vessey@xxxxxxxxxx> wrote:

> (1)  What's the largest number of "logical processors" that Xen supports
> on the host system?  For me, this translates to cores.  I prefer to keep
> hyperthreading out of the picture.  (I believe that this was 126 in 3.3,
> but is changing to "unlimited" based on Jan Beulich's recent work.  Is
> that correct?)

The default build configuration is for 64 CPUs. You have to re-build Xen to
configure support for more CPUs than that. Yes, 126 is the limit for 3.3.

> (2a)  What's the largest host memory that anybody has tested?
> (2b)  What's the expected host memory limit (if somebody was able to
> configure a system that large)?

I think 256GB has been tested. Theoretically we're good up to 1TB, and we
could expand beyond even that without too much trouble.

> (3a)  What's the largest guest memory that anybody has tested?
> (3b)  What's the expected guest memory limit (if somebody was able to
> configure a system that large)?

I think 64GB guests are tested fairly often. There's no particular reason
that a guest couldn't use all available memory, whatever that is (except for
32-bit PV guests which are limited for arcane technical reasons).

> (4a)  Does Xen support hot-add of physical hardware to the host system?
> If so, which devices?
> (4b)  Hot remove?

Depends what the usage scenario of those devices is. One answer would be
that Xen supports device hotplug as far as dom0 supports it.

> (5a)  What's the maximum # of virtual NICs per guest?
> (5b)  What's the maximum # of virtual HBAs per guest?
> (5c)  What's the maximum # of LUNs per guest?
> (6)  What's the maximum # of powered-on guests per system?

Theoretically only limited by available resources. I don't know what's
actually been tested.

 -- Keir



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