[CentOS] Question about storage for virtualisation

Fajar Priyanto
Tue, 26 Jun 2012 01:17:36 -0000

On Tue, Jun 26, 2012 at 9:05 AM, Nicolas Ross
<rossnick-lists at cybercat.ca> wrote:
> I have some general questions about VM.
>
> If I set vcpu let's say to 2-3 for a single vm, does this mean that
> those CPU are dedicated to that vm or many vm can share the same
> physicial cpus ?
No, all the CPU will be virtualized and shared.
Although there is "affinity" option where physical CPU is locked to a
certain VM. But in general this option gives more bad effect than
good.

> So, I was wondering what's the best for managing storage for VMs ? I
see
> mostly recomandations for LV for storing VM's disks. It seem to helps
to
> create snapshots for backup purposes. Is this the fastest way of
> creating backups ? And will data access be faster that if I use regular
> files ?
Using LV will give you flexibility among other things. Better have it
in the beginning rather than sorry later (e.g. running out of space,
etc).
The performance difference is insignificant.

> In my case, the "main" setup of each vm is rather simple. The
minimal
> OS, updates, my own httpd, my own php a couple of other packages. So
> restoring a VM from scratch can take less than an hour. So I was
> thinking of not taking snapshot of the whole VM and only sync the data
> partition.
That's ok.

> As for the guest paritions, I am accustomed of separating my servers
> disks with separate /, /usr, /var, /home and /data partitions. I can't
> recall today why I started doing this, 15 years ago, but I still like it
> that way and continue to do so. Do I still "need" to do this with
VMs ?
The reason of creating separate partitions is mainly for security and
preserve data during reinstallation.
I believe it's still good to do your way.


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