diff --git a/libexec/rc/rc.conf b/libexec/rc/rc.conf
--- a/libexec/rc/rc.conf
+++ b/libexec/rc/rc.conf
@@ -359,6 +359,7 @@
 nfs_server_enable="NO"		# This host is an NFS server (or NO).
 nfs_server_flags="-u -t"	# Flags to nfsd (if enabled).
 nfs_server_managegids="NO"	# The NFS server maps gids for AUTH_SYS (or NO).
+nfs_server_maxio="131072"	# Maximum I/O size for the nfsd.
 mountd_enable="NO"		# Run mountd (or NO).
 mountd_flags="-r -S"		# Flags to mountd (if NFS server enabled).
 weak_mountd_authentication="NO"	# Allow non-root mount requests to be served.
diff --git a/libexec/rc/rc.d/nfsd b/libexec/rc/rc.d/nfsd
--- a/libexec/rc/rc.d/nfsd
+++ b/libexec/rc/rc.d/nfsd
@@ -28,6 +28,12 @@
 	# oids are available.
 	load_kld nfsd || return 1
 
+	if [ -n "${nfs_server_maxio}" ]; then
+		if ! sysctl vfs.nfsd.srvmaxio=${nfs_server_maxio} >/dev/null; then
+			warn "Failed to set server max I/O"
+		fi
+	fi
+
 	if checkyesno nfs_reserved_port_only; then
 		echo 'NFS on reserved port only=YES'
 		sysctl vfs.nfsd.nfs_privport=1 > /dev/null