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RE: [Xen-users] (no subject)

  • To: jdbb@xxxxxxx, xen-users@xxxxxxxxxxxxxxxxxxx
  • From: "Petersson, Mats" <Mats.Petersson@xxxxxxx>
  • Date: Mon, 3 Apr 2006 18:10:15 +0200
  • Delivery-date: Mon, 03 Apr 2006 09:11:10 -0700
  • List-id: Xen user discussion <xen-users.lists.xensource.com>
  • Thread-index: AcZXGQvJZ4ASTaB4TIK5svIrvfjXSwAHpQ9A
  • Thread-topic: [Xen-users] (no subject)

 > -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> jdbb@xxxxxxx
> Sent: 03 April 2006 13:19
> To: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-users] (no subject)
> Hi,
> regarding an internal setup for a workgroup of about 20 
> people, I'm thinking about the stability of xen 3.x at the 
> moment? It's all about uptimes here as there are long time 
> computations running on the server and the users would be 
> quite annoyed of reboots.
> So, how stable is xen and xend at the moment? Any uptimes, 
> any experiences someone?

Sorry, can't answer this properly, as I'm a Xen HV developer, and my machine 
rarely runs much more than 48 hours before I reboot it to try some different 
version of hypervisor... Quite often, I'll reboot it more than 5 times in the 
same day... Particularly when working on bugs... 

But I believe there are people out there running Xen 3.0 for much longer than 
me - but it's only been out since early January [I think], so obviously uptimes 
of more than about 100 days would be pretty much impossibly - today, in three 
months time I'd expect it to be close to 200 days on the "best" machines. 

> How much Ram do you keep for Dom0 on multiuser setups? In 
> terms of overhead, disk cache etc. Would 20 x 384 MB be ok on 
> a 8192 MB Host?

20 users would need more than 4 processors to get some heavy (long) 
calculations finished in reasonable time, so I'd be happy to guess that you 
actually want at least two machines anyways, unless of course you say that only 
a few of them are allowed to run their calculations at any given time, in 
either case your 20 x 384MB isn't really a valid case any longer. 

Whilst giving Dom0 some more memory is a good thing, it probably won't make a 
huge difference on the system's performance if you go beyond 1GB for Dom0 - 
cache performance is a case of "diminishing returns - the cost (memory size) 
doubled gives only a small benefit", once you've gone past a certain point 
(around 256MB, I would say - but I haven't benchmarked it). 

> How's PAE Support? Any Problems with more than 4 GB Ram?

Why not use 64-bit hypervisor and guests? It would make more sense to me. But 
you can use PAE if you want. Essentially 64-bit support is based on PAE, so it 
should work just fine for either case. I know 64-bit is pretty close to stable 
at this time. 

> Regards,
> Karl
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