openstack team mailing list archive

[Anne Gentle <anne@xxxxxxxxxxxxx>]

Hi Alexey  -
Glad you were able to get some answers on IRC. Looks quite thorough,
and not all these concepts are easily explained in the frozen/static
written word. :) Sometimes videos and one-on-one discussions will
serve you better. But of course we want to continuously improve docs
so this feedback is welcome.

More responses embedded below.


On Sun, Feb 19, 2012 at 11:16 PM, Alexey Eromenko <al4321@xxxxxxxxx> wrote:
> Hello all,
>
> Anne: You were recommended contact by Todd Deshane ("deshantm" on IRC)
> about this issue.
>
> The problem:
> I'm new to OpenStack and while learning it, all of it's concepts seem wild.
>
> I have read the OpenStack Getting Started Guide PDF (from
> docs.openstack.org), but it doesn't explain the most basic concepts.

For the Starter Guide, log your feedback on this project specifically:
http://bugs.launchpad.net/openstackbook.

> Things like:
> 1. Why Object Storage (swift) vs. Network File System (NFS)
> =============================================
> According to: "notmyname"
> <notmyname> technologov: the things that object storage in general
> (and swift specifically) provides is large scale, cheap, and durable
> storage
>
> <notmyname> technologov: object storage is all about relaxing some of
> the constraints of a posix-style system. for example, if you don't
> have to provide atomic operations (ie you can rely on eventual
> consistency), you can much more easily scale a storage system and not
> have a central point of failure
>
> Also:
> I have seen a video, that explains a bit about hashing searches, but
> very incomplete.
> Also what happens if new servers get added or removed ?
> Such concepts need to be added into the docs.

A link to the video in the bug you log would be useful to the authors.

> Does Object Storage also stores files ? (seems yes)

Yes. Lots of web devs use object storage to store and serve static
images on websites. There are also archiving use cases.

> 2. Nova vs Images (glance) vs. Object Storage (swift)
> =============================================
>
> Both (1) Nova-volume and (2) glance and (3) swift seem capable of
> storing VM hard disks.
> What's the conceptual difference between the three ?
> Possible Answer:
> "<notmyname> technologov: nova-volume is for block storage attached to
> a VM. glance is to manage the VM images in a nova cluster and provide
> nice ways of storing them (a bridge to the storage, not the storage
> itself). swift is an object storage system that can be used by glance
> or on its own. swift isn't a filesystem, so it's not "mountable" like
> the devices managed with nova-volume"
>
> Arguments & Discussion:
> <technologov> come on... "mountable" term is a joke... nowadays you
> can mount GMail or Wikipedia... via FUSE
> <technologov> w.p. is not a Filesystem either :)
>
> <notmyname> ok, so you don't use swift like a traditional hard drive.
> the only access to it is API-based (and the API is http)
> <notmyname> that can be wrapped into a FUSE filesystem (but there are
> big tradeoffs in doing so--advantages too, of course)
>
> Once we can agree on the concepts, need to patch official docs.

Would welcome patches. Conceptually speaking, you're coming at it from
a point of transition in the history of the project. Nova-volume
hasn't yet been replaced but several storage solutions want to offer
"plugins" - there is no documentation about how to configure those
yet, but it is a priority for Doc Day March 6th. [1] Nova-volume
offers storage to virtual images running in nova. Glance is
specifically for image storage. Swift is specifically for object
storage.


> 3. Minimal OpenStack setup for new developers to get started is ?
> =============================================
> Nova only ? Glance and Swift are optional modules, right?
>
> I'd be glad to help to improve docs, but I don't understand those
> concepts myself.

>From my view point, most people want a Dashboard. That said, I don't
believe that OpenStack is all about Compute only, either. Them's
fightin' words. Okay, not really, :) but believe me, storage is more
important to some as a minimal install than computing power. You can't
really make that decision of best "minimal" for people.

Devstack.org is the best starting point for new Python devs,
Trystack.org is the best starting point for new API devs. These are
the suggested starting points.

> More docs issues:
> =============================================
> 4. Hierarchies & terminology:
> How do you call Live-migration-domain in OpenStack lingo ? (group of
> hosts, where virtual machines can be live-migrated from one to the
> next)
> Are there any other types of domains / virtual machine groups / host
> machine groups in OpenStack concept / terminology ?

Not that I know of, but others may have a different opinion here. I'd
like the list's input on this item specifically, please?

> 5. Cross-platform host OS support:
> Currently the heavy use of "iptables" mandates Linux host. This
> assumption is true if you only support KVM, Xen, LXC, OVZ, UML.
> With a possible future port of OpenStack to VirtualBox engine, this
> assumption is false.
> 5.a. Is "iptables" mandatory or optional ?
> 5.b. What other OpenStack features exist that may fail on FreeBSD
> hosts ? And on Windows hosts ?
>
> NOTE: I'm OK if OpenStack effort stays Linux-only, but this must be
> clearly documented, along with portability hints.

Hm. Not sure of the best approach here. Please log this as a specific
bug for http://bugs.launchpad.net/openstack-manuals and the doc team
can discuss (all are welcome to that discussion).

> 6. Also Dashboard GUI was not covered in getting started PDF, which
> seems important.

This book, the Starter Guide, goes with the Ubuntu server, and the
addition of Object Storage was just this past revision. Hopefully
these suggestions can get into the next round. Because the guide is
written to a specific Ubuntu version, and that version did not ship
with Dashboard, it does not include Dashboard instructions. Please log
this against the openstackbook project. It'll be improved in the next
release of Ubuntu server.

> 7. Security: Remote VM control is secured ? How ? Libvirtd ?
> (From my quick look it seems that nova connects to remote
> nova-compute, not to libvirtd.)

Could someone from the nova team please address this question? I'm not
qualified.

> 8. Which other important concepts might I miss ?

Your new eyes are great for helping us improve the documentation.
Please keep the conceptual questions coming.

Thanks,
Anne



>
> --
> -Alexey Eromenko "Technologov", 20.02.2012.

[1] http://www.mail-archive.com/openstack@xxxxxxxxxxxxxxxxxxx/msg07456.html