diff --git a/servers/puppet/modules/humbug/files/postgresql/30-postgresql-shm.conf.master b/servers/puppet/modules/humbug/files/postgresql/30-postgresql-shm.conf.master
deleted file mode 100644
index cec73b374e..0000000000
--- a/servers/puppet/modules/humbug/files/postgresql/30-postgresql-shm.conf.master
+++ /dev/null
@@ -1,13 +0,0 @@
-# Shared memory settings for PostgreSQL
-
-# Note that if another program uses shared memory as well, you will have to
-# coordinate the size settings between the two.
-
-# Maximum size of shared memory segment in bytes
-#kernel.shmmax = 33554432
-
-# Maximum total size of shared memory in pages (normally 4096 bytes)
-#kernel.shmall = 2097152
-
-kernel.shmall = 6553600
-kernel.shmmax = 26843545600
diff --git a/servers/puppet/modules/humbug/files/postgresql/40-postgresql.conf.master b/servers/puppet/modules/humbug/files/postgresql/40-postgresql.conf.master
new file mode 100644
index 0000000000..c24b37e081
--- /dev/null
+++ b/servers/puppet/modules/humbug/files/postgresql/40-postgresql.conf.master
@@ -0,0 +1,16 @@
+# Shared memory settings
+
+# Maximum total size of shared memory in pages (normally 4096 bytes)
+kernel.shmall = 6553600
+# Maximum size of shared memory segment in bytes
+kernel.shmmax = 26843545600
+
+# Virtual memory settings
+vm.swappiness = 0
+vm.overcommit_memory = 2
+
+# We don't want these numbers to be too large or else performance
+# will be too spiky.  These seem to give a good balance between low
+# numbers and sequential write performance
+vm.dirty_ratio = 5
+vm.dirty_background_ratio = 2
diff --git a/servers/puppet/modules/humbug/files/postgresql/30-postgresql-shm.conf.slave b/servers/puppet/modules/humbug/files/postgresql/40-postgresql.conf.slave
similarity index 54%
rename from servers/puppet/modules/humbug/files/postgresql/30-postgresql-shm.conf.slave
rename to servers/puppet/modules/humbug/files/postgresql/40-postgresql.conf.slave
index 92062b609d..a883175e58 100644
--- a/servers/puppet/modules/humbug/files/postgresql/30-postgresql-shm.conf.slave
+++ b/servers/puppet/modules/humbug/files/postgresql/40-postgresql.conf.slave
@@ -1,13 +1,14 @@
 # Shared memory settings for PostgreSQL
 
-# Note that if another program uses shared memory as well, you will have to
-# coordinate the size settings between the two.
-
-# Maximum size of shared memory segment in bytes
-#kernel.shmmax = 33554432
-
 # Maximum total size of shared memory in pages (normally 4096 bytes)
-#kernel.shmall = 2097152
-
 kernel.shmall = 1703936
+# Maximum size of shared memory segment in bytes
 kernel.shmmax = 6979321856
+
+# Virtual memory settings
+vm.swappiness = 0
+vm.overcommit_memory = 2
+
+# These are the defaults on newer kernels
+vm.dirty_ratio = 10
+vm.dirty_background_ratio = 5
diff --git a/servers/puppet/modules/humbug/manifests/postgres-common.pp b/servers/puppet/modules/humbug/manifests/postgres-common.pp
index e7216b71b6..eec9ccc4b3 100644
--- a/servers/puppet/modules/humbug/manifests/postgres-common.pp
+++ b/servers/puppet/modules/humbug/manifests/postgres-common.pp
@@ -14,8 +14,8 @@ class humbug::postgres-common {
   }
 
   exec { "sysctl_p":
-    command   => "/sbin/sysctl -p /etc/sysctl.d/30-postgresql-shm.conf",
-    subscribe => File['/etc/sysctl.d/30-postgresql-shm.conf'],
+    command   => "/sbin/sysctl -p /etc/sysctl.d/40-postgresql.conf",
+    subscribe => File['/etc/sysctl.d/40-postgresql.conf'],
     refreshonly => true,
   }
 
diff --git a/servers/puppet/modules/humbug/manifests/postgres-master.pp b/servers/puppet/modules/humbug/manifests/postgres-master.pp
index c9133ea957..90c6f4e8bc 100644
--- a/servers/puppet/modules/humbug/manifests/postgres-master.pp
+++ b/servers/puppet/modules/humbug/manifests/postgres-master.pp
@@ -4,12 +4,17 @@ class humbug::postgres-master {
   $master_packages = [ "xfsprogs", "mdadm", ]
   package { $master_packages: ensure => "installed" }
 
+  # We bundle a bunch of other sysctl parameters into 40-postgresql.conf
   file { '/etc/sysctl.d/30-postgresql-shm.conf':
+    ensure => absent,
+  }
+
+  file { '/etc/sysctl.d/40-postgresql.conf':
     ensure => file,
     owner  => 'root',
     group  => 'root',
     mode   => 644,
-    source   => 'puppet:///modules/humbug/postgresql/30-postgresql-shm.conf.master',
+    source   => 'puppet:///modules/humbug/postgresql/40-postgresql.conf.master',
   }
 
   file { "/etc/postgresql/9.1/main/postgresql.conf":
diff --git a/servers/puppet/modules/humbug/manifests/postgres-slave.pp b/servers/puppet/modules/humbug/manifests/postgres-slave.pp
index 734d0bc347..108f7f4a1a 100644
--- a/servers/puppet/modules/humbug/manifests/postgres-slave.pp
+++ b/servers/puppet/modules/humbug/manifests/postgres-slave.pp
@@ -1,12 +1,17 @@
 class humbug::postgres-slave {
   class { 'humbug::postgres-common': }
 
+  # We bundle a bunch of other sysctl parameters into 40-postgresql.conf
   file { '/etc/sysctl.d/30-postgresql-shm.conf':
+    ensure => absent,
+  }
+
+  file { '/etc/sysctl.d/40-postgresql.conf':
     ensure => file,
     owner  => 'root',
     group  => 'root',
     mode   => 644,
-    source   => 'puppet:///modules/humbug/postgresql/30-postgresql-shm.conf.slave',
+    source   => 'puppet:///modules/humbug/postgresql/40-postgresql.conf.slave',
   }
 
   file { "/etc/postgresql/9.1/main/postgresql.conf":