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On Saturday, August 02, 2025 11:19:23 PM Charles Curley wrote: > On Sat, 2 Aug 2025 21:56:34 -0400 > rhkramer@gmail.com wrote: > > On Thursday, July 31, 2025 08:42:27 AM Charles Curley wrote: > > > * Set up high availability between the two kea servers. > > > > What do you mean by that? > > https://kea.readthedocs.io/en/stable/arm/hooks.html#libdhcp-ha-so-high-avai > lability-outage-resilience-for-kea-servers
Ahh, ok, thanks!
Aside: sometimes I like to (over?) simplify some things -- the referenced page is useful, it describes various forms of redundancy like:
"The Kea HA hook library supports three configurations, also known as HA modes: load-balancing, hot-standby, and passive-backup. In the load-balancing mode, two servers respond to DHCP requests."
Those are somewhat self descriptive, but I'd add a little bit:
Aside: note that I'll say because DHCP leases are persisistent, that complicates things a little -- I try to address in these notes:
* load-balancing / sharing with failover (in normal operation two (or more, iiuc) servers share the load, if one (and maybe more than one, as long as there is one left) fails, the other server(s) take over the full load with a possible cost in performance. Servers advise each other about the leases they open / create so that on failure of one server, the other has the information about open leases which it needs to continue.
* hot-standby: one server does the job, but sends information about the leases it opens / creates to a (hot) backup server so that if the "working" server fails, the hot-standby has the information it needs to continue to do the job
* passive-backup: not completely clear to me at the moment, so I won't try to describe
I'll also mention that there is a somewhat technical reason why they call these modes "high-availability" instead of redundancy, which I did not immediately grasp and didn't (and won't) bother to try to understand, at least atm.
Aside: I guess the reason I asked my question in the first place is because the phrasing of the statement: (~"high availability *between* the servers") seemed a little unusual / awkward to me -- I might have said something more like "high availability provided by multiple servers".
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