Goal A reliable server configuration which serves as the off-site backup for several, distributed servers as well as hosting a few virtual machines. Each server's backups should be encrypted, incremental and de-duplicated. The virtual machines are relatively low in resource requirements (all taken together ~2 GB RAM, 100 GB storage), and need to be administered remotely. The final configuration needs to be able to withstand one or two hard-drive failures. Replacement of failed hard-drives does not need to happen online, but should be simple enough (e.g. identify failed drive, replace with clean drive of same capacity, boot, wait for rebuild). The system should be able to detect and remedy Bitrot.
Hardware I would like to employ an HP N54L, 8GB ECC RAM, 4 x 4TB WD RED, 2 x 120 GB TOSHIBA disks. I also have an HP P410 controller which I could use, if that is the best option.
Plan My current idea is to use the 4 x 4 TB as software or hardware RAID 5 for storage of backups and VMs, 2 x 120 GB as hardware RAID 1 for the OS/hypervisor. Install Debian, set up Proxmox VE 4 on top, one VM for BorgBackup plus additional VMs.
File systems ZFS might eat up too much RAM to run reliably especially since there will also be some VMs, BTRFS does not offer bitrot detection if you use the nodatacow-option to counter bad performance for VMs. Ext4 does not offer protection from Bitrot.
Which filesystem can I employ?