29 Dec
2011
29 Dec
'11
1:47 p.m.
On 12/29/2011 04:34 PM, Andrew Cathrow wrote: > > ----- Original Message ----- >> From: "Itamar Heim"<iheim@redhat.com> >> To: "Miki Kenneth"<mkenneth@redhat.com> >> Cc: engine-devel@ovirt.org >> Sent: Thursday, December 29, 2011 5:41:41 AM >> Subject: Re: [Engine-devel] SPM Priority Design - Wiki Page >> >> On 12/27/2011 05:22 PM, Miki Kenneth wrote: >>> Few points: >>> - From requirement perspective - 0-10 scale is OK too. >>> - There is an RFE to allow manual SPM selection, let's make sure >>> that we clarify how we do that in the scenarios. >>> - There is a case were all Hosts are set as "no SPM" (-1), user >>> should be notify (on the last host?) > I don't agree with/understand the requirements > <snip> > - Enable setting a priority between -1 and 100 for a host (100 is the highest, -1 means never to choose this host). > - When SPM selection process takes place, use the SPM priority to select an SPM. > - Default for upgrading ovirt will be 50. > </snip> > > Here we are asking the user to define priorities for the SPM selection. A user should be able to influence the selection but the actual choice should come down to runtime status. > If Host A us running 100 VMs and host B is running 50 then it seems more efficient for B to be the SPM rather than A > If Host C has multiple storage paths to the LUN then it seems a better fit than host B that has only one path. > > We need to step back and review the requirements here. > > Today SPM selection is random, that certainly needs to change but a user defining priorities is overly complex and won't solve the runtime selection issue. > > We need to start by defining an algorithm for selecting the SPM independent of user input. > At selection time I'd suggest that we at least need to consider number of paths to the storage (for block based) number of VMs on that host, perhaps #cores? Paths to which storage domain? the master? all? on average? Do you prefer 2x10Gb iSCSI connection, or 4x1Gb? - What about available bandwidth to the storage (assuming it may be capped and compete with VM IO traffic) ? - Latency? > Perhaps we should dynamically create a score for a host that takes these factors into account, each may get higher rating - eg. maybe # storage paths is more important that # cores ? This is why I've suggested High(8)-Med(5)-Low(2) and add dynamically the system scoring, with whatever params we get to eventually. 'Never' could be 0, 'Always' could be '10'. Y. > > > On top of this we can add some user defined preference that plays into the score. For example a user can say "this host can NEVER be an SPM" or can set a preference - eg. "Preferred SPM" or perhaps even "always SPM" > > This algorithm would apply for automated selection of SPMs but a user should be allowed to override this and at runtime say "make this node the SPM now" > > > >> SPM is DC level, not cluster level. >> >>> - Need to be able to view in the GUI: >>> - the SPM priority for all Hosts, on the GRID? >> isn't this cluttering the hosts grid? general subtab maybe? >> _______________________________________________ >> Engine-devel mailing list >> Engine-devel@ovirt.org >> http://lists.ovirt.org/mailman/listinfo/engine-devel >> > _______________________________________________ > Engine-devel mailing list > Engine-devel@ovirt.org > http://lists.ovirt.org/mailman/listinfo/engine-devel