Hi Andre, I think what you really want to look at is stretch mode. There have been long discussions on this list why a crush rule with rep 4 and 2 copies per DC will not handle a DC failure as expected. Stretch mode will make sure writes happen in a way that prevents split brain scenarios. Hand-crafted crush rules for this purpose require 3 or more DCs. Best regards, ================= Frank Schilder AIT Risø Campus Bygning 109, rum S14 ________________________________________ From: Janne Johansson <icepic.dz@gmail.com> Sent: Wednesday, November 20, 2024 11:30 AM To: Andre Tann Cc: ceph-users@ceph.io Subject: [ceph-users] Re: Crush rule examples
Sorry, sent too early. So here we go again: My setup looks like this:
DC1 node01 node02 node03 node04 node05 DC2 node06 node07 node08 node09 node10
I want a replicated pool with size=4. Two copies should go in each DC, and then no two copies on a single node. How can I describe this in a crush rule?
This post seem to show that, except they have their root named "nvme" and they split on rack and not dc, but that is not important. https://unix.stackexchange.com/questions/781250/ceph-crush-rules-explanation... with the answer at the bottom: for example this should work as well, to have 4 replicas in total, distributed across two racks: step take default class nvme step choose firstn 2 type rack step chooseleaf firstn 2 type host -- May the most significant bit of your life be positive. _______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-leave@ceph.io