Re: [Xen-users] LVM?

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> I'm just starting with XEN and I've few basic questions.
> My last goal is build a system with dom0 CentOS-based and domU
> CentOS-based too.
>
> So...
>
> 1) ¿Is LVM filesystem managment recommended? The CentOS partitioner uses
> LVM by default, but I can disable it manually. ¿Offers LVM any
> advantatge over tradictional partition system?

LVM is more flexible - you can easily create a new logical volume for each 
guest's virtual disk.  You can distribute guest disks across multiple 
physical volumes, etc etc.  Good stuff for management and it should perform 
well too.

Running LVM in the guests isn't really that useful, though and makes it harder 
to access guest filesystem contents from dom0.  I'd suggest you just use LVM 
on the host.

Using normal files as the backing storage for guests is good for playing 
around.  Use tap:aio rather than file: mode to access this storage is 
preferred - tap tackles some unpleasant problems with the file: mode which 
uses the loop-device (nb. I'm talking about paravirt domains, things are a 
little different for HVM domains).

LVM is probably the best storage solution for a production machine, unless you 
decide to use a SAN or something like that...

> 2) Same question about SELinux.

I think RHEL / CentOS 5 has an SELinux setup that's designed to work OK with 
Xen.  If you use file-backed images you have to put them in a specific 
directory or it'll complain.  I don't know how SELinux would interact with 
LVM-based volumes, though.

I'm not sure how useful SELinux is for a Xen dom0 because I'm not sure what 
RHEL / CentOS put in their default config.  You could use it for confining 
other services, but you shouldn't really be running services in dom0 
anyhow...

Running SELinux in guests has all the same benefits of running it on a native 
machine though, so you should definitely consider that if it fits your 
usecase.

HTH,
Cheers,
Mark

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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