josephineSei
commented
2 days ago In todays IaaS call, we discussed a few open questions:
Network AZ
In the standard I discussed, that it is possible to have Network AZ, but this has downsides for users. Thus i did not make any recommendations. We discussed, whether we even want to discourage CSPs to use it ("SHOULD NOT"):
- it has been brought up that it is hard to configure and not nice to use for users
- @garloff: discourage or even forbid usage of network AZs
- @berendt: should not be forbidden, there are use cases
- These are really not nice for users, we should discourage it (but not disallow)
- ToDo: Ask for more use cases, maybe we can not even discourage
Cross-Attach AZ
Question was, whether we want to encourgage / allow / discourage or disallow this?
- so far, nearly no CSP uses this according to Hedgedoc input
- @garloff: unlike for network it is not obvious that I can attach volumes from other AZs
- when using Ceph, you'd normally have a global cross-AZ for storage (but not several storage AZs)
- if not using Ceph, implementation would be hard, we should not request this from CSPs
- Use-case wavecon: Local dedicated (per AZ) ceph clusters, no support for x-attaching
- @artificial-intelligence: X-attach would negatively impact isolation between AZs (and performance)
- Maybe transparency is the most important feature here?
- important to distinguish between replicating storage between AZs vs. cross-attaching volumes across AZs
Overall
- We can not define all kinds of details how DCs should be built for highest availability
- Reference DC taxonomies / BSI taxonomy for this
- SCS can be useful by providing some minimal bounds that allows uses to have meaningfully higher chance to survive by spreading over several AZs
- Highest level of redundancy will always be achieved by replicating data over several regions
- Can we define something with "AZ"s that's better than nothing (though never as good as regions)?
horazont
closes #539