Hi,
- Can we have multiple pools in a stretch cluster?
yes, you can have multiple pools, but apparently they have to be all
configured with the stretch rule as you already noted.
- Can we have multiple different crush rules in a stretch cluster?
It's still a regular ceph cluster, so you can have different crush
rules. But the stretch mode requires a specific one so your other
rules probably won't be covered by the stretch mode. I haven't had the
chance to test the stretch mode on a real cluster yet, so I'm not
really sure if it actually supports only one rule. But we've built
stretched clusters without the actual stretch mode with previous
releases, it's basically just a matter of crush rules so your
resiliency rerequirements are met. Just remember that you need a third
monitor as a tiebreaker. I would assume that if you configure your
cluster with the stretch mode you'll have the advantages of the
stretch mode for those pools configured with the strech rule (OSD to
OSD communication within one DC), but other DC aware rules would still
apply and ensure the configured resiliency. So that would result in
some form of mixed mode or something.
Regards,
Eugen
Zitat von Eneko Lacunza <elacunza@xxxxxxxxx>:
Hi all,
We're looking to deploy a stretch cluster for a 2-CPD deployment. I
have read the following docs:
https://docs.ceph.com/en/latest/rados/operations/stretch-mode/#stretch-clusters
I have some questions:
- Can we have multiple pools in a stretch cluster?
- Can we have multiple different crush rules in a stretch cluster?
I'm asking this because the command for stretch mode activation asks
for a rule...
We want to have different purpose pools on this Ceph cluster:
- Important VM disks, with 2 copies in each DC (SSD class)
- Ephemeral VM disks, with just 2 copies overall (SSD class)
- Backup data in just one DC (HDD class).
Objective of the 2-DC deployment is disaster recovery, HA isn't
required, but I'll take it if deployment is reasonable :-) .
Alternative would be a size=4/min=3 pool for important VM disks in a
no-strech cluster...
Thanks
Eneko Lacunza
Zuzendari teknikoa | Director técnico
Binovo IT Human Project
Tel. +34 943 569 206 |https://www.binovo.es
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