Re: a few may be wiki question

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Farkas Levente wrote:
> hi,
> i try to setup a centos host server with kvm and a few guest os for the
> first time. imho there is only a very limited docs about kvm (even if i
> try to read them:-). so there are a few general questions:
> - which is the recommended host config?:
>   - should i used x86_64 or i386 host kernel? i don't know in advance,
>     but probably most guest os will be 32 bit. is there any advantage or
>     disadvantage to use x86_64 as a host os?
>   

If you have more than 1GB of RAM, 64-bit will be slightly faster.  
Otherwise there is no preference.

>   - i'll use kernel-2.6.18-8.1.8.el5, but i read in the announcement
>     for kvm-34:
>     "running on a host earlier than Linux 2.6.23-rc2 will experience
>      a slight performance degradation"
>     what does exactly means and how much is the "slight"? or if i use
>     older kernel it's better to use kvm-33?
>   

It's likely not measurable for most uses.  It's recommended to always 
use the latest kvm version in order to get the latest fixes and 
enhancements.

>   - i read in faq 3.6:
>     "for the host. 1GB is probably a minimum configuration for the host
>      OS."
>     does this means i have to reserve 1GB for the host os?
>   

No.  That is the total amount of RAM on the host (and it's a 
recommendation -- you can work with less if you like).

>     it's strange for me just because eg with xen dom0 we use 256MB and
>     it was enough since dom0 don't have any real load. it's not the case
>     with kvm?
>   

It depends on what the host is doing.  If it isn't running any workload, 
even 128MB should be enough.

>     who much ram should i use for the guest os?
>   

That's for you to choose; select as much memory as the guest needs and 
you can give it.

>     eg if i use 6 guest then i need at least 6GB of ram?
>   

If each guest gets 1GB, yes.  But you can give guests less memory.

>   - is dynamic use of RAM for host operating system supported?
>   

What's that?

>   - what is the recommended size for the host disk partition?
>   

Whatever is sufficient for your distro.  I use 10GB usually (FC6/F7).

>   - what is the recommended swap partition size for the host os ?
>   

The regular recommendation of your distro.  Size of RAM is usually ok.

> - which is the recommended guest config?
>   - what is the recommended memory for a guest os? same as i would run
>     natively?
>   

Yes.  Depending on workload and budget.

>   - what is the recommended guest disk image format? should i use an lvm
>     partition as guest os partition (like in xen)? what is the
>     recommended format assuming that may be later i'd like to add new
>     guests and what is the performance differences (ie. which is the
>     fastest format)?
>   

Depends on workload.  lvm is fastest, qcow2 is most flexible and 
managable.  If your guest is not issuing significant disk I/O, I'd 
recommend qcow2.  Otherwise lvm.

>   - what is the recommended swap partition format and size for the
>     guest os ?
>   

Whatever is recommended by the guest OS vendor.

> - what is the current general state of kvm ie. stability, performance
> support etc? i mean for non mission critical production server it's
> worth to choose in stead of xen or not?
>   

I find it very stable.  Try it out!

> i know most of my questions are too general, but almost all answer will
> start as "it's depend on.." but still a general guideline would be useful.
>
> last but not least may be a kvm-user list would be useful where such
> questions can send and not disturbing all the developers.
>   

Well, my stance on this is that if a user needs to send such an email, 
then the application or documentation is missing and should be fixed.  
The developers need to be bothered until the situation is corrected.  
Having a users list is just a cover up for bad usability and documentation.

I regard this type of email as valuable feedback, not disturbance.

[now back to not writing documentation]

-- 
error compiling committee.c: too many arguments to function


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