[one-users] Storage subsystem: which one?

Humberto N. Castejon Martinez humcasma at gmail.com
Thu Oct 13 02:03:59 PDT 2011


I have a setup with a shared-NFS solution for managing VM images. In my
current setup, I share the whole /srv/cloud directory between the front-end
and the worker nodes. One thing I do not like from this solution is that VM
images take space from all workers, even if a worker is not executing a
certain VM.

I wonder if there exist more efficient solutions. Some potential
alternatives I have looked at are: using ZFS/NexentaStor as shared
centralized storage or MooseFS  as shared distributed storage. However, I am
quite new to both Opennebula and storage solutions, so I would appreciate if
you could help me to understand the benefits and disadvantages of these
alternatives (as well as other potential ones).
tored (i.e. whether they are stored in the workers themselves or not).

Reading the Opennebula documentation, I believe there are two things I have
to deal with:

1) The image repository, and whether it is shared or not between the
front-end and the workers
2) The <VM_DIR>, that contains deployment files, etc for the VMs running on
a worker. This directory may or not be shared between the front-end and the
workers, but it should always be shared between the workers if we want live
migration, right?

Some of the questions I have are these (sorry if some of them seem stupid

- What are the implications of sharing or not the image repository  between
the front-end and the workers (apart from the need to transfer images to the
worker nodes in the latter case)?
- What are the implications of sharing or not the <VM_DIR> between the
front-end and the workers?
- Can I use ZFS or MooseFs and still be able to live migrate VMs?
- Will the <VM_DIR> always hold a (copy of a) VM image for every VM running
on a worker? Must the <VM-DIR> be in the local hard drive of a worker or may
it reside on an external shared storage?

I guess two factors i should also consider when choosing a solution are the
following, right?

- The speed of transferring VM images
- The speed of cloning VM images

Thanks for your help!

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