----- Original Message ----- > From: "Avra Sengupta" <aseng...@redhat.com> > To: "Lalatendu Mohanty" <lmoha...@redhat.com>, "Raghavendra Bhat" > <rab...@redhat.com>, "gluster-devel" > <gluster-devel@nongnu.org>, "Rahul Hinduja" <rhind...@redhat.com>, "Seema > Naik" <sen...@redhat.com> > Sent: Wednesday, April 16, 2014 11:39:11 AM > Subject: Re: [Gluster-devel] autodelete in snapshots > > 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.
Agreed with Avra, the purpose of introducing soft limits and hard limits was to restrict snap creation to reach limit+1 at any point in time. Any time the limit reaches the hard limit the subsequent creation should fail. Once the limit reaches the soft limit the auto-delete starts in background. Since soft-limit is configurable option between 1-100, it really gives flexibility to the user to start the auto-deletion based on his requirement it can be at 1% or even 100% soft-limit. If the auto-delete option is set to true than it should be triggered and should log message based on user's input of soft-limit and if it is set to false the auto-delete should only log message and snap creation fails when it reaches the hard-limit. Thanks, Rahul > > Regards, > Avra > > On 04/15/2014 07:18 PM, Lalatendu Mohanty wrote: > > > On 04/15/2014 07:05 PM, Raghavendra Bhat wrote: > >> > >> Hi, > >> > >> As of now, in snapshots there are 2 limits for the number of > >> snapshots, hard-limit and soft-limit. Usually soft-limit is 90% of > >> hard-limit by default (it can be changed also). Say the hard-limit is > >> 50, then soft-limit by default will be 45. We are planning to do > >> autodelete of the oldest snapshot upon reaching the limit. > >> > >> There are 2 options: > >> > >> 1) Start doing autodelete upon reaching the soft-limit. i.e If the > >> hard limit is 50 and the number of the snapshots taken becomes 45, > >> then for the next snapshot taken (i.e 46th snapshot), the oldest > >> snapshot will be automatically deleted in the background. > >> > >> 2) Use soft-limit as a means to notify the admin about limit being > >> reached (gf_log, syslog etc, or also a warning message shown for > >> every snapshot taken after the soft limit is reached) and start doing > >> autodelete after reaching the hard-limit i.e once 50 snapshots are > >> reached, then when 51st snapshot is triggered, the oldest snapshot > >> will be deleted in the background. > >> > >> Please provide feedback. > > > > I like the #2 option. If user has set something as hard-limit, it > > should be treated as hard limit and soft-limit can be used as warning > > mechanism. > > > >> > >> NOTE: The auto-delete can be made configurable, which if turned off, > >> snapshot create fails upon reaching the limit. > >> > >> Regards, > >> Raghavendra Bhat > >> > >> _______________________________________________ > >> Gluster-devel mailing list > >> Gluster-devel@nongnu.org > >> https://lists.nongnu.org/mailman/listinfo/gluster-devel > > > > > > _______________________________________________ > > Gluster-devel mailing list > > Gluster-devel@nongnu.org > > https://lists.nongnu.org/mailman/listinfo/gluster-devel > > _______________________________________________ Gluster-devel mailing list Gluster-devel@nongnu.org https://lists.nongnu.org/mailman/listinfo/gluster-devel
