hi!
thanks to all of you, I appreciate this very much! I will have to go through
all of your messages a few more times and do some research.
so our rule from the intial post does make sure, that, when 1 room goes down it
does NOT try to restore 3 replicas in the remaining room but it will only
> so size 4 / min_size 2 would be a lot better (of course)
More copies (or parity) are always more reliable, but one quickly gets into
diminishing returns.
In your scenario you might look into stretch mode, which currently would
require 4 replicas. In the future maybe it could support EC
thank you Robert!
this sounds like split brain again... but we have a quorum system by using 3
monitor nodes. so only the room with the majority of the ceph-mons is available
for I/O.
if the room with the majority of the ceph-mons is the one that is cut-off, I
suppose we'd need to do this:
go
great, thank you Anthony! :)
so size 4 / min_size 2 would be a lot better (of course)
we have to stay at 3/2 for now though, because our OSDs are filled 60% in sum
maybe someone can answer additional questions:
- what is the best practice to avoid a full OSD scenario, where ceph tries to
This is not speculation: I have personally experienced this with an inherited
2R cluster.
> On Mar 3, 2023, at 04:07, Janne Johansson wrote:
>
>
> Do not assume the last PG needs to die in a horrible fire, killing
> several DC operators with it, it only takes a REALLY small outage, a
> fluke
Den fre 3 mars 2023 kl 01:07 skrev :
> it is unclear for us what min_size means besides what it does. i hope someone
> can clear this up :)
> someone pointed out "split brain" but I am unsure about this.
>
> i think what happens in the worst case is this:
> only 1 PG is available, client writes
On 02.03.23 09:16, stefan.pin...@bearingpoint.com wrote:
so if one room goes down/offline, around 50% of the PGs would be left with only
1 replica making them read-only.
Most people forget the other half of the cluster in such a scenario.
For us humans it is obvious that one room is down,
> but what is the problem with only one active PG?
> someone pointed out "split brain" but I am unsure about this.
I think Paxos will ensure that split-brain doesn’t happen by virtue of needing
>50% of the mon quorum to be up.
> i think what happens in the worst case is this:
> only 1 PG is
