[ovirt-devel] Gluster Volume Snapshots - Feature review

Shubhendu Tripathi shtripat at redhat.com
Wed Dec 31 05:56:44 UTC 2014

Hi Einav,

Find the comments inline.

Thanks and Regards,

On 12/30/2014 11:13 PM, Einav Cohen wrote:
> Thank you, Shubhendu! I have a few more comments:
>> Yes that's true for most of the cases. But having Options setting from
>> sub-tab, not sure if that's correct. May be "New" is fine.
> I think that if a user already got to the "Snapshots" sub-tab of a
> specific Volume, it would seem strange that not all Snapshots-related
> actions for that Volume are available from there - but I will leave it
> to your discretion; I think that "New" is indeed the most important one
> to have also in the sub-tab.

We may have the New option available under sub tab as well. Setting 
configuration options would only be available in Volumes main tab.

>> Once scheduled the only way to stop snapshot creation is to provide an
>> end date.
> let me try and understand what are the exact snapshot creation capabilities.
> consider the following use-cases (which may make absolutely no sense,
> just giving these as examples in order to understand the capabilities):
> (1) let's say that I want to do two recurring snapshots schedules in
> parallel for a single volume: one Monthly, and another one Weekly.
> Can I do that?

We can have only one schedule for a volume at a time.

> I am assuming that I can't, i.e. there can only be one recurring-snapshot-
> creation schedule per volume (which you create via "New" and edit via
> "Schedule") - is that correct? If so: are you blocking an attempt to
> create a "New" recurring snapshot schedule when one already exists for
> this Volume (e.g. disable the "New" button, fail a CanDoAction with a
> message such as "Cannot create snapshot scheduling. A snapshot scheduling
> already exists for this Volume", etc.) or allowing override of the already-
> existing schedule (with a proper warning)?

Even if a volume snapshot creation is scheduled user can still opt for 
onetime spot snapshot creation and New would be available.

> If my assumption is wrong, and I can have two (or more) recurring-
> snapshot-creation schedules per volume: how do I *edit* these schedules?
> what happens when I click on "Schedule"? which one of the two schedules
> will I edit? The Weekly one? The Monthly one?

As there is only one schedule for a volume at a time, so this is not 
valid scenario. Exiting single instance of schedule can be edited using 
the option Volumes -> Snapshots -> Schedule. May be if you suggest this 
option can be renamed to "Edit Schedule".

> If I am comparing the terminology to the one of Calendar meeting schedule
> (see http://i.imgur.com/xvf5w30.png): I don't have any "series" objects
> that I can 'edit', I can see only "instances", and I can edit only one
> "global" 'series' object via the "Schedule" button.
> [again: if there can only be one recurring-snapshot-creation schedule per
> volume, then the current design is OK, assuming the attempt to create a
> second snapshot-schedule for a volume is properly blocked/overridden/...]

Yes, attempt to create second snapshot schedule is actually an override 
option. Of course spot creation is allowed in addition to the scheduled.

> (2) let's say that I want to do a weekly recurring snapshot scheduling for
> a certain volume. In addition to that weekly recurring snapshots, I want
> to take a one-time snapshot of this volume right now. Can I do that?

Yes, as discussed above stop one time creation in addition to the 
scheduled is allowed.

> If so: then my suggestion [http://i.imgur.com/4j7hvRY.png, option 3] is
> indeed valid; I am assuming that the user can create, per volume: one
> recurring snapshot schedule + unlimited one-time snapshots.

Yes. That's correct.

> [If the user can create two (or more) recurring snapshot schedules - see
> (1) above].
> need to make sure that the user is able to create a "New" snapshot with
> the "Weekly" recurrence schedule, and then another "New" snapshot(s) with
> the "None" recurrence schedule, which will create the one-time snapshot(s)
> immediately, and that the schedule of the Weekly snapshot can be edited
> via the "Schedule" option.

So it goes like this. Say a Weekly snapshot is scheduled for certain 
volume and later user wants to create single on-spot snapshot. For this 
he/she need to select the option Volumes -> Snapshots -> New and not 
Volumes -> Snapshots -> Schedule. By default the option None is selected 
as Recurrence type and it creates a one time snapshot. Still the 
schedule stands valid in the system and if the user wants to edit the 
schedule he/she need to select the option Volumes -> Snapshots -> 
Schedule. Hope this clarifies.

> If not (i.e. the user can create only one recurring snapshot schedule,
> and that's it - no additional recurring snapshot schedules, no one-time
> immediate snapshots, etc.), then my suggestion is invalid, and a 'None'
> recurrence is not needed.

As said above, one time snapshot creation is still allowed in addition 
to the scheduled. (Using Volumes -> Snapshots -> New option)

> In this case, just need to make sure that the 'Schedule' side-section of
> the dialog will be pre-populated with the most common/reasonable recurrence
> schedule, in case the user will not touch it.
> BTW, if this is indeed the case, then there is probably no need for both
> 'New' and 'Schedule' buttons - only 'Schedule' is sufficient.
>> Accept. The snapshot create dialog itself can be used here.
> Just need to make sure to change its title accordingly (to 'Schedule
> Snapshot' or something similar; right now it says "New Snapshot" in
> the wiki).
> I assume that this dialog can be used for:
> (a) creating a New snapshot schedule (which should look very similar
> to the 'New Snapshot' dialog, maybe with some pre-populated values,
> maybe without the 'None' option in the Recurrence drop-down).

If the option Volumes -> Snapshots -> New selected, the dialog opens 
with pre-populated snapshot name prefix and Recurrence type selected as 
None by default. This effectively is one time snapshot creation.
If this is first time and user wants to schedule the snapshot creation, 
he/she can change the recurrence type and provide details. Snapshot 
creation is scheduled in this case.
Later, it user wants to edit the schedule, he/she needs to select option 
Volumes -> Snapshots -> Schedule (may be for this reason only I want to 
call it Edit Schedule). So effectively option Volumes -> Snapshots -> 
Schedule is meant for only re-scheduling the snapshot creation. If its 
not yet scheduled dialog opens with recurrence type selected as None.

> - and/or -
> (b) editing the already-existing schedule (in this case, fields that
> cannot be edited should be disabled).

As above.

> I hope I was clear - please let me know if you have any questions or
> comments.
> Thanks again!
> ----
> Regards,
> Einav
> ----- Original Message -----
>> From: "Shubhendu Tripathi" <shtripat at redhat.com>
>> To: "Einav Cohen" <ecohen at redhat.com>
>> Cc: devel at linode01.ovirt.org, "rhsc-dev" <rhsc-dev at redhat.com>
>> Sent: Tuesday, December 30, 2014 7:09:51 AM
>> Subject: Re: [ovirt-devel] Gluster Volume Snapshots - Feature review
>> Thanks Einav for the detailed review and your comments.
>> Find below the comment inline.
>> Will update the wiki accordingly and circulate.
>> Team, please provide your thoughts (if conflicting) on this.
>> Thanks and Regards,
>> Shubhendu
>> On 12/30/2014 05:33 AM, Einav Cohen wrote:
>>> Hi Shubhendu,
>>> First of all - very detailed wiki pages (I focused mainly on the
>>> User Experience part) - nicely done.
>>> I have a couple of comments / suggestions regarding the GUI:
>>> Snapshot action-group:
>>> - from the wiki page:
>>> """
>>> A new action-group "Snapshot" would be introduced under actions
>>> for a volume.
>>> """
>>> I assume that you will implement it similarly to the "Power Management"
>>> action-group (on Hosts main tab) or the "Profiling" action-group (on
>>> the Volumes tab), i.e. with a drop-down-like styling
>>> [http://i.imgur.com/eWRg6o8.png]?
>> Yes. That's correct.
>>> - If the Snapshot-related actions are expected to be core/critical in
>>> the Volumes-related workflows, it makes sense to put them in the main-
>>> tab, but please consider adding them to the Snapshots sub-tab as well,
>>> in order to be consistent with other similar oVirt workflows.
>> Yes that's true for most of the cases. But having Options setting from
>> sub-tab, not sure if that's correct. May be "New" is fine.
>>> New Snapshot dialog -> Schedule section:
>>> - I suggest to implement the time-interval selection with a drop-down,
>>> rather than a radio-button group; it is more consistent with e.g.
>>> event-repeat scheduling in a calendar [http://i.imgur.com/y9Gn3wq.png],
>>> it will save real-estate within the dialog and it will be more easily
>>> readable for the user.
>> That's a good suggestion. Will do this.
>>> - to my understanding, the New Snapshot functionality doesn't have to
>>> be recurrent; however, there isn't any way to "disable" the recurring
>>> aspect. Here are some suggestions to how this should be added:
>>> http://i.imgur.com/4j7hvRY.png
>> Once scheduled the only way to stop snapshot creation is to provide an
>> end date.
>>> Option 3 is my personal favorite - it is the simplest, and is consistent
>>> with Calendear-scheduling UI. Option 1 is my least favorite, however it
>>> is consistent with e.g. the "Enable Power Management" UI within the "New
>>> Host" dialog.
>> Option-3 looks good to me as well. Should be doable I feel.
>>> Snapshots -> Options:
>>> - I think that there are a couple of problematic issues with this dialog:
>>>     * the different functionality of this dialog when a Volume is selected
>>> vs. when no Volume is selected may be unclear to the user.
>> Agree
>>>     * the fact that we can update Cluster-related parameters (which
>>> potentially affects *all* volumes in that Cluster) within a specific
>>> Volume-context dialog is a bit risky - and we don't have anything similar
>>> to that anywhere in the application today IIRC.
>>> my recommendations:
>>>     * have separate "Options - Cluster" and "Options - Volume" actions;
>>> "Options - Cluster" should always be enabled.
>>> "Options - Volume" should be enabled only when a Volume is selected.
>> Accept
>>>     * Seehttp://i.imgur.com/pfRpjrH.png  for my suggestion for "Cluster
>>> Options" vs. "Volume Options". Note that from the "Volume Options"
>>> dialog, you may allow editing the Cluster Options by clicking on the
>>> link-button, which will either (a) open the "Cluster Options" dialog
>>> on top or (b) allow editing the Cluster Values inline within the
>>> already-open dialog - this should be accompanied with a clear note to
>>> the user that he is editing Cluster-related parameters from the current
>>> (Volume) context, which may affect *all* Volumes in that Cluster.
>>> Also note that in my suggestion, the user can conveniently see both the
>>> Volume values and the Cluster Values side-by-side at once, for reference.
>> Accept
>>> Snapshots -> Schedule:
>>> - to my understanding, this should be very similar (or identical) to the
>>> New Snapshot functionality? if so, we may want to simply open the "New
>>> Snapshot" dialog focused on the "Schedule" side-section (rather than the
>>> 'General' side-section, maybe already pre-populated with some values in
>>> the 'General' side-section (which will still be editable by the user) and
>>> something already pre-selected in the (focused) "Schedule" section.
>>> please let me know whether you think these can/should be incorporated
>>> into the design, and/or if you have any comments or questions.
>> Accept. The snapshot create dialog itself can be used here.
>>> thanks.
>>> ----
>>> Regards,
>>> Einav
>>> ----- Original Message -----
>>>> From: "Shubhendu Tripathi"<shtripat at redhat.com>
>>>> To:devel at linode01.ovirt.org,jhernand at redhat.com, "Michael
>>>> Pasternak"<mpastern at redhat.com>
>>>> Sent: Monday, November 10, 2014 1:52:40 AM
>>>> Subject: [ovirt-devel] Gluster Volume Snapshots - Feature review
>>>> Hi All,
>>>> Please help us to review the design of Gluster Volume Snapshots in oVirt,
>>>> Here are two design on wiki page
>>>> General Feature Design
>>>> http://www.ovirt.org/Features/GlusterVolumeSnapshots
>>>> Detailed Design
>>>> http://www.ovirt.org/Features/Design/GlusterVolumeSnapshots
>>>> We target it in ovirt 3.6 release.
>>>> Marked Juan/Michael specifically for REST review.
>>>> Best Regards,
>>>> Shubhendu Tripathi
>>>> _______________________________________________
>>>> Devel mailing list
>>>> Devel at ovirt.org
>>>> http://lists.ovirt.org/mailman/listinfo/devel

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