[ILUG] Xen: Dividing RAM between dom0 and domU's[Scanned]

[Barry Flanagan]

Sam Johnston wrote:
> You probably want to leave it at 128Mb for your domU's but try not to
> starve
> dom0 (1/2 gig should be fine). I suspect the main factor here will be the
> file system cache - dom0 does the dirty work on behalf of the domU's so one
> would think that the larger the cache the better. I'm not sure what's
> involved in tuning this though (nor whether any is required).
> 

I always leave 256 for dom0 and that has proved fine with up to 10 domUs
(uptimes of over a year for heavily loaded systems). I would say 512Mb
is overkill.

-Barry


> - samj
> 
> On 11/1/06, Cormac McClean <cormac.mcclean at gmail.com> wrote:
>>
>> Hi,
>>
>> Thanks to all who emails with assitance regarding setting up Xen on the
>> DELL PowerEdge 2850. I got it working with Debian Etch/Sid and the
>> packages xen-linux-system-2.6.18-1-xen-686 and
>> xen-hypervisor-3.0.3-1-i386
>> .
>>
>> I have one further question relating to the allocation of RAM to the
>> domU's. I have 3.5 GBs of RAM (potentially 4GB but I don't want to risk
>> messing up a working setup to recompile the kernel for the extra 0.5GB)
>> and I have 20 domUs (possibly asking for trouble, but I want each
>> student to have his/her own virtual server). I have allocated 128MB to
>> each of the domU's, leaving 1109MB for dom0 (of which currently 261 is
>> used and 847 free with the 20 domU's running). Should I allocate more to
>> dom0? I could reduce the RAM for the domU's to 64MB each, which would
>> effectively double the RAM for dom0, but is this a waste? How important
>> is RAM to dom0?
>>
>> Any advice on this would be appreciated.
>>
>> Regards,
>> Cormac.
>>
>> -- 
>> Cormac McClean.
>> Lecturer, Athlone IT Software Engineering
>> Free/Open Source Software Enthusiast
>>
>> Please avoid sending me Microsoft Word or PowerPoint attachments.
>> See http://www.gnu.org/philosophy/no-word-attachments.html
>>
>>
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-- 

-Barry Flanagan