Linux Guests

Linux Guest on BTRFS:

• BTRFS with single copy of meta, system and data
• I/O is better on modern guest Kernel 6.1 (vs 5.10)
• I/O is better whem VM storage is “no cache”
  • sync writes goes to ZFS ZIL
  • With “Writeback” cache - ZFS ZIL was not utilized so high like with “no cache”

Block sizes:

• Default zvol volblocksize was 8k
• Latest Proxmox creates zvols with 16k volblocksize

So it is best to fit guest block sizes into ZFS block (16k) sizes:

• mkfs.btfs options: –nodesize 16k
• btrfs mount options: -o noatime
• mkfs.ext4 options: -b 4096 -E stride=4,stripe-width=8
• ext4 mount options: -o noatime,user_xattr