[Engine-devel] alias in disk instead of name

Mon Oct 22 08:50:02 UTC 2012

----- Original Message -----
> From: "Michael Pasternak" <mpastern at redhat.com>
> To: "Simon Grinberg" <simon at redhat.com>
> Cc: "engine-devel" <engine-devel at ovirt.org>
> Sent: Monday, October 22, 2012 8:58:25 AM
> Subject: Re: [Engine-devel] alias in disk instead of name
> 
> On 10/21/2012 06:13 PM, Simon Grinberg wrote:
> > 
> > 
> > ----- Original Message -----
> >> From: "Michael Pasternak" <mpastern at redhat.com>
> >> To: "Simon Grinberg" <simon at redhat.com>
> >> Cc: "engine-devel" <engine-devel at ovirt.org>
> >> Sent: Sunday, October 21, 2012 4:56:33 PM
> >> Subject: Re: [Engine-devel] alias in disk instead of name
> >>
> >> On 10/21/2012 04:15 PM, Simon Grinberg wrote:
> >>>
> >>>
> >>> ----- Original Message -----
> >>>> From: "Michael Pasternak" <mpastern at redhat.com>
> >>>> To: "Simon Grinberg" <simon at redhat.com>
> >>>> Cc: "engine-devel" <engine-devel at ovirt.org>
> >>>> Sent: Sunday, October 21, 2012 3:48:46 PM
> >>>> Subject: Re: [Engine-devel] alias in disk instead of name
> >>>>
> >>>> On 10/21/2012 03:36 PM, Simon Grinberg wrote:
> >>>>>
> >>>>> ----- Original Message -----
> >>>>>>> From: "Michael Pasternak" <mpastern at redhat.com>
> >>>>>>> To: "engine-devel" <engine-devel at ovirt.org>
> >>>>>>> Sent: Sunday, October 21, 2012 12:26:46 PM
> >>>>>>> Subject: [Engine-devel] alias in disk instead of name
> >>>>>>>
> >>>>>>>
> >>>>>>> The problem we caused by using alias in disk instead of name
> >>>>>>> is
> >>>>>>> break
> >>>>>>> of search-by-name paradigm
> >>>>>>> in engine.search dialect, not sure why we do not want forcing
> >>>>>>> disk
> >>>>>>> name to be unique [1],
> >>>>>>> but lack of "name" in disk search is does not look good in my
> >>>>>>> view.
> >>>>>>>
> >>>>>>> thoughts?
> >>>>>>>
> >>>>>>> [1] can be easily achieved via appropriate can-do-action
> >>>>>>> verification.
> >>>>> Names by definition are not unique IDs,
> >>>>
> >>>> they do, otherwise /search wasn't effective, remember users not
> >>>> exposed to entity id, all entities fetched by-name, so names has
> >>>> to
> >>>> be unique.
> >>>
> >>> Yap that is what we do with many entities, and it causes
> >>> problems.
> >>> But with disks it is multiplied
> >>>
> >>>>
> >>>>> thus it should not be enforced.
> >>>>> What would be the auto naming conversion to ensure uniqueness
> >>>>> with
> >>>>> plain text?
> >>>>
> >>>> not sure i follow, i'll assume you refer here to empty name, -
> >>>> you
> >>>> cannot have an
> >>>> entity with no name.
> >>>
> >>> Well you create a new disk - do we want to enforce the user to
> >>> provide a unique disk name/alias for every disk he creates?
> >>> This will drive the user crazy. This is important even for user
> >>> only for floating/shared disks. For any other disks user does not
> >>> care if it's disk1, hd1, whatever. For these kind of disk, it's
> >>> just a VM disk and the user does not care if in all VMs this is
> >>> called disk 1 - so why bother him?
> >>
> >> from the same reason we have unique
> >> clusters/datacenters/networks/templates/etc...
> > 
> > Networks, DataCenter, Clusters, templates - are in order of
> > magnitude less then the number of disks.
> > And you name once and use many.
> > 
> > As for VMs - well it's may take that we should not force uniqueness
> > either ( you can warn though )
> 
> you cannot have two vms with same name in same domain ...

I didn't say that in a domain you are allowed to have two guests with the same hostname, I've said engine should allow for having duplicate VM names.
You are assuming that the VM name is identical to the guest host name. 

For many this is the case, for other it's just an alias/name given in oVirt. 
Actually for the cloud, this is mostly going to be the case and worse, you are blocking different tenants from having the same VM name just because you are assuming that VM name = guest hostname.  

> 
> > 
> > For disks, well number is >= VMs to >>>= VMs
> > Name by definition is mostly interesting in many cases only within
> > the VM, and we don't even have a way to correlate disk alias to
> > the internal name in the VM. In many cases as said before, a user
> > won't care about the name/alias if it is always attached to the
> > same VM. A user will rather look the VM and then list it's disk.
> > So actually I'll be better off with vm1.disk1 vm2.disk2 then
> > unique name per disk (PS AFAIK) this should be the default
> > suggested name by the UI, but then changing the VM name will break
> > this (yes, I know it's not possible ATM, but many people I know
> > requested for that).
> > 
> > So I as user will prefer that all the disks that created from a
> > template will have the same name as the original template, and
> > then to be able to search by (vm=name, disk=name) thus I can
> > access easily the same disk for the VMs.
> > 
> > On the other hand for others, as you've mentioned (especially for
> > floating and shared disk) the name/alias may be of importance,
> > uniqueness may be very important.
> 
> any disk can become shared.

Then when you make it shared then bother to give it a meaningful alias

> 
> > 
> > All that I'm saying that we can't force it's not that uniqueness in
> > never desired.
> 
> simon, you missing the point, i was talking about /search,
> search is available only at /api/disks (i.e shared disks,
> vm/template.disks is
> irrelevant to this discussion)

Nope I do not, but I think that our perspectives differ.
You are looking at it as strictly design issue. You have a collection of entities and you want a human readable search, thus you are trying to force (rightfully) from your point of view a unique alias/name for those. 

I taking the end user perspective, and user experience 
1. Majority of the disks have no meaning outside of a VM scope.
2. There are fractions of the disks that are usually shared (this is the nature of shared disks)
3. There are fractions of floating, most of the floating will be a transient state, while you are moving disks around. 

What I'm trying to say that forcing a user to provide a unique name per disk is a huge bother. 
And again in the multi tenancy case, you can't enforce a unique alias in the system.

What will you say to the user in the error message? 
Sorry you can't use this alias since another user that is sharing the system with you already provided that name? And yes we know you can't see that other disk, and it you don't care about the other user, but still you can't use your alias since this is how our platform designed.

The meaning is that you must allow a for a more sophisticated search. Yes even in the context of the disks tab. Disks are not really stand alone entities, and if we keep to strict conventions like - in any collection an entity name must be unique, then you are making the system hardly usable for many users. 

So a search in disks should include other 'properties' (and yes I know those are not disk properties, but this is how a user will look at it) like owner,quota,vm,storage domain, etc. 

To some up - what should be unique are UUIDs of an entities, and infrastructure entities names (within the same scope) - all the rest must not.

> 
> > 
> >>
> >>>    
> >>>>
> >>>>> Would you change these on import/export?
> >>>>
> >>>> would you mind elaborating on this?
> >>>
> >>> Yes,
> >>>
> >>> You are already facing a problem when importing VMs that already
> >>> have the same name, now you increasing the problem for disks that
> >>> have the same alias. for same name we force clone if you want to
> >>> import. Why for clone just because of a disk alias (this implies
> >>> collapse snapshots ATM) or even bother the user with renaming
> >>> disks that he does not care about the name so he just gave disk
> >>> 1,
> >>> 2, 3 and so on?
> >>
> >> i see your point, but then we leave no option for the user to
> >> locate
> >> the disk,
> >> simply because he doesn't have unique identifier,
> >>
> >> just imagine user A creating disk and calling it X,
> >> then user B creating disk and calling it X, they on different
> >> domains etc., and now both want to use disk X,
> >>
> >> how they can figure out which one to pick?, by SD, by size? agree
> >> this is doesn't look well..., even more than that - someone may
> >> call
> >> this "bad design"...
> > 
> > This is why the search should accept more then the name.
> > Example (vm=name, disk=name/alias)
> > Example (dc=name, disk=name/alias)
> > Example (sd=name, disk=name/alias)
> 
> it's not about accepting both name/alias, it's about missing ability
> to identify your resource in collection.
> 
> > For floating/shared on the same SD/DC/VM I would suggest a warning
> > if there is a duplicate in the system - not enforcement.
> 
> ok, lets assume we WARN user that his disk's name is not unique, how
> user will pick the unique name?
> implementing own code checking if new name (he wants to use) is
> unique or not?
> 
> - this is business logic, not user's prerogative.
> 
> > There is a difference between best practice and being enforcing up
> > to the level that it annoys some of the users.
> 
> simon, when you register to email, you have to try N times till you
> find unique username,
> is it convenient? absolutely NO, is it annoying? YES, but you forced
> doing that so
> system will be able to identify you,
> 
> it's no different in any way, good software protects user/itself even
> in cost of convenience,
> 
> bottom line
> ===========
> 
> - i think as long as disk not shared/floating it can have any name
> - in a minute disk designation changed to shared, name uniqueness
> should be forced (by the engine)
> - when importing vm with shared disks, name uniqueness should be
> forced
> - when creating vm from template with shared disk, name uniqueness
> should be forced
> - alias should be changed back to name (in sake of consistency)
> - /api/disks collection should support searching disks by name (in
> sake of consistency)
> 
> 
> thoughts?

Please look at the previous comment, that just can't work in the multi-tenancy case.
Name should not be unique, the warning is for the admin only, from the user portal a warning should be issues only if the user provides same name twice.

> 
> > 
> >>
> >>
> >> --
> >>
> >> Michael Pasternak
> >> RedHat, ENG-Virtualization R&D
> >> _______________________________________________
> >> Engine-devel mailing list
> >> Engine-devel at ovirt.org
> >> http://lists.ovirt.org/mailman/listinfo/engine-devel
> >>
> 
> 
> --
> 
> Michael Pasternak
> RedHat, ENG-Virtualization R&D
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