[ovirt-devel] Gluster Volume Snapshots - Feature review

Shubhendu Tripathi shtripat at redhat.com
Wed Dec 31 06:00:21 UTC 2014

Small typo error corrected.

On 12/31/2014 11:26 AM, Shubhendu Tripathi wrote:
> Hi Einav,
> Find the comments inline.
> Thanks and Regards,
> Shubhendu
> 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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