Hi all. We are searching for information about how to size dovecot servers in a clustered architecture (dovecot + postfix + roundcube + mysql). We need to migrate mailboxes from an old Exchange installation: 60k mailbox 900 GB total storage 14 MB/mailbox About 133 email/mailbox Low usage: about 2k simultaneous imap/pop3 connections This is how we are thinking to build our new architecture 3 x Dell R630 or R530 servers with 6x300SAS disks for Ceph storage with 1 replica . Total storage = 2,5 TB for mailboxes 3 x Dell R630 or R530 with 2x CPU 6core,64GB RAM, 4x 300SAS disks hosting the following VMs in a VMware cluster: - 3 x VM Dovecot - 3 x VM Postfix - 3 x VM Roundcube webmail - 3 x VM MySQL All VMs are behind a balancer All OS disks are on local storage Dovecot VMs share Ceph storage with OCFS2 filesystem for the mailboxes. I'd like to have some hints about CPU and memory for Dovecot VMs. 2 vCPU and 8 GB RAM each sould be enough? Is there a way to calculate this? Do you think the storage performance could be a problem using Ceph + OCFS2? Is Ceph + XFS + Dsync replication a better choice? Thanks! Michele