Hi We currently have a 3 DC setup with 6 HDD servers in each of 3 DCs, running replica 3 and EC 4+5 pools. This works fine for mostly dormant data but of course not so well for other stuff requiring low latency etc. Mostly big RBDs shared by kernel NFS with a bit of CephFS. We want to start migrating some of these big RBD backed NFS shares to NVMe. We currently have 3 E3.S servers, one in each DC, with an EC 4+5 pool with DC->OSD crush selection. We are wondering how to cheapest increase redundancy short term since we do not have enterprise money. With what we have we can lose 1 DC (aka host in this case) and 1 OSD and still be online, but there's nowhere to backfill and some hardware problems, like a faulty mainboard or CPU can take down an entire "DC". Ideally we would have several more hosts in each DC so we had DC->Host->OSD but that's not an option. I am thinking it could make sense to add just 1 more server in a 4th DC and keep the 4+5 rule as is, simply giving us a buffer of 1 more failed host before we hit problems. Thoughts? Mvh. Torkil -- Torkil Svensgaard Sysadmin MR-Forskningssektionen, afs. 714 DRCMR, Danish Research Centre for Magnetic Resonance Hvidovre Hospital Kettegård Allé 30 DK-2650 Hvidovre Denmark Tel: +45 386 22828 E-mail: torkil@drcmr.dk