[Gluster-devel] autodelete in snapshots

Vijay Bellur vbellur at redhat.com
Wed Apr 23 00:20:41 UTC 2014

On 04/20/2014 11:42 PM, Lalatendu Mohanty wrote:
> On 04/16/2014 11:39 AM, Avra Sengupta wrote:
>> The whole purpose of introducing the soft-limit is, that at any point
>> of time the number of
>> snaps should not exceed the hard limit. If we trigger auto-delete on
>> hitting hard-limit, then
>> the purpose itself is lost, because at that point we would be taking a
>> snap, making the limit
>> hard-limit + 1, and then triggering auto-delete, which violates the
>> sanctity of the hard-limit.
>> Also what happens when we are at hard-limit + 1, and another snap is
>> issued, while auto-delete
>> is yet to process the first delete. At that point we end up at
>> hard-limit + 1. Also what happens
>> if for a particular snap the auto-delete fails.
>> We should see the hard-limit, as something set by the admin keeping in
>> mind the resource consumption
>> and at no-point should we cross this limit, come what may. If we hit
>> this limit, the create command
>> should fail asking the user to delete snaps using the "snapshot
>> delete" command.
>> The two options Raghavendra mentioned are applicable for the
>> soft-limit only, in which cases on
>> hitting the soft-limit
>> 1. Trigger auto-delete
>> or
>> 2. Log a warning-message, for the user saying the number of snaps is
>> exceeding the snap-limit and
>> display the number of available snaps
>> Now which of these should happen also depends on the user, because the
>> auto-delete option
>> is configurable.
>> So if the auto-delete option is set as true, auto-delete should be
>> triggered and the above message
>> should also be logged.
>> But if the option is set as false, only the message should be logged.
>> This is the behaviour as designed. Adding Rahul, and Seema in the
>> mail, to reflect upon the
>> behaviour as well.
>> Regards,
>> Avra
> This sounds correct. However we need to make sure that the usage or
> documentation around this should be good enough , so that users
> understand the each of the limits correctly.

It might be better to avoid the usage of the term "soft-limit". 
soft-limit as used in quota and other places generally has an alerting 
connotation. Something like "auto-deletion-limit" might be better.


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