appliance: Add sensible disk optimizations.

The timeout lets us read remote images without timing out.

The noop scheduler lets the host do scheduling.  This generally makes
sense for mixed workloads because the host has a global view of the
system, and often has more compute power too.

appliance/init

@@ -83,6 +83,12 @@ if grep -sq selinux=1 /proc/cmdline; then
   mount -t selinuxfs none /sys/fs/selinux
 fi
 
+# Disk optimizations.
+# Increase the SCSI timeout so we can read remote images.
+for f in /sys/block/sd*/device/timeout; do echo 300 > $f; done
+# https://access.redhat.com/site/solutions/5427
+for f in /sys/block/[hsv]d*/queue/scheduler; do echo noop > $f; done
+
 # Update the system clock.
 hwclock -u -s