diff --git a/packages/xo-server-load-balancer/src/index.js b/packages/xo-server-load-balancer/src/index.js
index ce7311e05..75a4ad7ca 100644
--- a/packages/xo-server-load-balancer/src/index.js
+++ b/packages/xo-server-load-balancer/src/index.js
@@ -25,10 +25,6 @@ const debug = LOAD_BALANCER_DEBUG
 const PERFORMANCE_MODE = 0
 const DENSITY_MODE = 1
 
-const LOW_BEHAVIOR = 0
-const NORMAL_BEHAVIOR = 1
-const AGGRESSIVE_BEHAVIOR = 2
-
 // Delay between each ressources evaluation in minutes.
 // Must be less than MINUTES_OF_HISTORICAL_DATA.
 const EXECUTION_DELAY = 1
@@ -40,6 +36,7 @@ const DEFAULT_CRITICAL_THRESHOLD_CPU = 90.0
 // Memory threshold in MB.
 const DEFAULT_CRITICAL_THRESHOLD_MEMORY_FREE = 64.0
 
+// Thresholds factors.
 const HIGH_THRESHOLD_FACTOR = 0.85
 const LOW_THRESHOLD_FACTOR = 0.25
 
@@ -79,22 +76,6 @@ export const configurationSchema = {
             ]
           },
 
-          behavior: {
-            type: 'object',
-
-            properties: {
-              low: { type: 'boolean' },
-              normal: { type: 'boolean' },
-              aggressive: { type: 'boolean' }
-            },
-
-            oneOf: [
-              { required: ['low'] },
-              { required: ['normal'] },
-              { required: ['aggressive'] }
-            ]
-          },
-
           pools: {
             type: 'array',
             description: 'list of pools id where to apply the policy',
@@ -118,6 +99,8 @@ export const configurationSchema = {
 
 // ===================================================================
 
+// Create a job not enabled by default.
+// A job is a cron task, a running and enabled state.
 const makeJob = (cronPattern, fn) => {
   const job = {
     running: false,
@@ -146,6 +129,23 @@ const makeJob = (cronPattern, fn) => {
   return job
 }
 
+// Compare a list of objects and give the best.
+function searchObject (objects, fun) {
+  let object = objects[0]
+
+  for (let i = 1; i < objects.length; i++) {
+    if (fun(object, objects[i]) > 0) {
+      object = objects[i]
+    }
+  }
+
+  return object
+}
+
+// ===================================================================
+// Averages.
+// ===================================================================
+
 function computeAverage (values, nPoints = values.length) {
   let sum = 0
   let tot = 0
@@ -204,28 +204,15 @@ function setRealCpuAverageOfVms (vms, vmsAverages) {
   }
 }
 
-function searchObject (objects, fun) {
-  let object = objects[0]
-
-  for (let i = 1; i < objects.length; i++) {
-    if (fun(object, objects[i]) > 0) {
-      object = objects[i]
-    }
-  }
-
-  return object
-}
-
 // ===================================================================
 
 class Plan {
-  constructor (xo, { name, mode, behavior, poolIds, thresholds = {} }) {
+  constructor (xo, name, poolIds, {
+    thresholds = {}
+  } = {}) {
     this.xo = xo
-    this._name = name // Useful ?
-    this._mode = mode
-    this._behavior = behavior
+    this._name = name
     this._poolIds = poolIds
-
     this._thresholds = {
       cpu: {
         critical: thresholds.cpu || DEFAULT_CRITICAL_THRESHOLD_CPU
@@ -251,29 +238,24 @@ class Plan {
     }
   }
 
-  async execute () {
-    if (this._mode === PERFORMANCE_MODE) {
-      await this._executeInPerformanceMode()
-    } else {
-      await this._executeInDensityMode()
-    }
+  execute () {
+    throw new Error('Not implemented')
   }
 
-  // =================================================================
-  // Performance mode.
-  // =================================================================
+  // ===================================================================
+  // Get hosts to optimize.
+  // ===================================================================
 
-  async _executeInPerformanceMode () {
+  async _findHostsToOptimize () {
     const hosts = this._getHosts()
     const hostsStats = await this._getHostsStats(hosts, 'minutes')
 
     // 1. Check if a ressource's utilization exceeds threshold.
     const avgNow = computeRessourcesAverage(hosts, hostsStats, EXECUTION_DELAY)
-    let exceededHosts = this._checkRessourcesThresholds(hosts, avgNow)
+    const toOptimize = this._checkRessourcesThresholds(hosts, avgNow)
 
     // No ressource's utilization problem.
-    if (exceededHosts.length === 0) {
-      debug('No ressource\'s utilization problem.')
+    if (toOptimize.length === 0) {
       return
     }
 
@@ -281,118 +263,15 @@ class Plan {
     const avgBefore = computeRessourcesAverage(hosts, hostsStats, MINUTES_OF_HISTORICAL_DATA)
     const avgWithRatio = computeRessourcesAverageWithWeight(avgNow, avgBefore, 0.75)
 
-    exceededHosts = this._checkRessourcesThresholds(exceededHosts, avgWithRatio)
-
-    // No ressource's utilization problem.
-    if (exceededHosts.length === 0) {
-      debug('No ressource\'s utilization problem.')
-      return
+    return {
+      toOptimize: this._checkRessourcesThresholds(toOptimize, avgWithRatio),
+      averages: avgWithRatio,
+      hosts
     }
-
-    // 3. Search the worst exceeded host by priority.
-    const toOptimize = searchObject(exceededHosts, (a, b) => {
-      a = avgWithRatio[a.id]
-      b = avgWithRatio[b.id]
-
-      return (b.cpu - a.cpu) || (a.memoryFree - b.memoryFree)
-    })
-
-    // 4. Search bests combinations for the worst host.
-    await this._optimize(
-      toOptimize,
-      filter(hosts, host => host.id !== toOptimize.id),
-      avgWithRatio
-    )
   }
 
-  async _optimize (exceededHost, hosts, hostsAverages) {
-    const vms = await this._getVms(exceededHost.id)
-    const vmsStats = await this._getVmsStats(vms, 'minutes')
-    const vmsAverages = computeRessourcesAverageWithWeight(
-      computeRessourcesAverage(vms, vmsStats, EXECUTION_DELAY),
-      computeRessourcesAverage(vms, vmsStats, MINUTES_OF_HISTORICAL_DATA),
-      0.75
-    )
-
-    // Compute real CPU usage. Virtuals cpus to reals cpus.
-    setRealCpuAverageOfVms(vms, vmsAverages)
-
-    // Sort vms by cpu usage. (higher to lower)
-    vms.sort((a, b) =>
-      vmsAverages[b.id].cpu - vmsAverages[a.id].cpu
-    )
-
-    const exceededAverages = hostsAverages[exceededHost.id]
-    const promises = []
-
-    const xapiSrc = this.xo.getXapi(exceededHost)
-
-    for (const vm of vms) {
-      // Search host with lower cpu usage.
-      const destination = searchObject(hosts, (a, b) =>
-        hostsAverages[b.id].cpu - hostsAverages[a.id].cpu
-      )
-      const destinationAverages = hostsAverages[destination.id]
-      const vmAverages = vmsAverages[vm.id]
-
-      // Unable to move the vm.
-      if (
-        exceededAverages.cpu - vmAverages.cpu < destinationAverages.cpu + vmAverages.cpu ||
-        destinationAverages.memoryFree < vmAverages.memory
-      ) {
-        continue
-      }
-
-      exceededAverages.cpu -= vmAverages.cpu
-      destinationAverages.cpu += vmAverages.cpu
-
-      exceededAverages.memoryFree += vmAverages.memory
-      destinationAverages.memoryFree -= vmAverages.memory
-
-      debug(`Migrate VM (${vm.id}) to Host (${destination.id}) from Host (${exceededHost.id})`)
-
-      // promises.push(
-      //   xapiSrc.migrateVm(vm._xapiId, this.xo.getXapi(destination), destination._xapiId)
-      // )
-    }
-
-    return
-  }
-
-  // =================================================================
-  // Density mode.
-  // =================================================================
-
-  async _executeInDensityMode () {
-    throw new Error('not yet implemented')
-  }
-
-  // =================================================================
-  // Check ressources.
-  // =================================================================
-
-  _checkRessourcesThresholds (objects, averages, mode = PERFORMANCE_MODE) {
-    if (mode === PERFORMANCE_MODE) {
-      return filter(objects, object => {
-        const objectAverages = averages[object.id]
-
-        return (
-          objectAverages.cpu >= this._thresholds.cpu.high ||
-          objectAverages.memoryFree <= this._thresholds.memoryFree.high
-        )
-      })
-    } else if (mode === DENSITY_MODE) {
-      return filter(objects, object => {
-        const objectAverages = averages[object.id]
-
-        return (
-          objectAverages.cpu < this._thresholds.cpu.low ||
-          objectAverages.memoryFree > this._thresholds.memoryFree.low
-        )
-      })
-    } else {
-      throw new Error('Unsupported load balancing mode.')
-    }
+  _checkRessourcesThresholds () {
+    throw new Error('Not implemented')
   }
 
   // ===================================================================
@@ -451,6 +330,145 @@ class Plan {
   }
 }
 
+// ===================================================================
+
+class PerformancePlan extends Plan {
+  constructor (xo, name, poolIds, options) {
+    super(xo, name, poolIds, options)
+  }
+
+  _checkRessourcesThresholds (objects, averages) {
+    return filter(objects, object => {
+      const objectAverages = averages[object.id]
+
+      return (
+        objectAverages.cpu >= this._thresholds.cpu.high ||
+        objectAverages.memoryFree <= this._thresholds.memoryFree.high
+      )
+    })
+  }
+
+  async execute () {
+    const {
+      averages,
+      hosts,
+      toOptimize
+    } = await this._findHostsToOptimize()
+
+    if (toOptimize.length === 0) {
+      return
+    }
+
+    const exceededHost = searchObject(toOptimize, (a, b) => {
+      a = averages[a.id]
+      b = averages[b.id]
+
+      return (b.cpu - a.cpu) || (a.memoryFree - b.memoryFree)
+    })
+
+    // 3. Search bests combinations for the worst host.
+    await this._optimize({
+      exceededHost,
+      hosts: filter(hosts, host => host.id !== exceededHost.id),
+      hostsAverages: averages
+    })
+  }
+
+  async _optimize ({ exceededHost, hosts, hostsAverages }) {
+    const vms = await this._getVms(exceededHost.id)
+    const vmsStats = await this._getVmsStats(vms, 'minutes')
+    const vmsAverages = computeRessourcesAverageWithWeight(
+      computeRessourcesAverage(vms, vmsStats, EXECUTION_DELAY),
+      computeRessourcesAverage(vms, vmsStats, MINUTES_OF_HISTORICAL_DATA),
+      0.75
+    )
+
+    // Compute real CPU usage. Virtuals cpus to reals cpus.
+    setRealCpuAverageOfVms(vms, vmsAverages)
+
+    // Sort vms by cpu usage. (higher to lower)
+    vms.sort((a, b) =>
+      vmsAverages[b.id].cpu - vmsAverages[a.id].cpu
+    )
+
+    const exceededAverages = hostsAverages[exceededHost.id]
+    const promises = []
+
+    const xapiSrc = this.xo.getXapi(exceededHost)
+
+    for (const vm of vms) {
+      // Search host with lower cpu usage.
+      const destination = searchObject(hosts, (a, b) =>
+        hostsAverages[b.id].cpu - hostsAverages[a.id].cpu
+      )
+      const destinationAverages = hostsAverages[destination.id]
+      const vmAverages = vmsAverages[vm.id]
+
+      // Unable to move the vm.
+      if (
+        exceededAverages.cpu - vmAverages.cpu < destinationAverages.cpu + vmAverages.cpu ||
+        destinationAverages.memoryFree > vmAverages.memory
+      ) {
+        continue
+      }
+
+      exceededAverages.cpu -= vmAverages.cpu
+      destinationAverages.cpu += vmAverages.cpu
+
+      exceededAverages.memoryFree += vmAverages.memory
+      destinationAverages.memoryFree -= vmAverages.memory
+
+      debug(`Migrate VM (${vm.id}) to Host (${destination.id}) from Host (${exceededHost.id})`)
+
+      // promises.push(
+      //   xapiSrc.migrateVm(vm._xapiId, this.xo.getXapi(destination), destination._xapiId)
+      // )
+    }
+
+    await Promise.all(promises)
+
+    return
+  }
+}
+
+// ===================================================================
+
+class DensityPlan extends Plan {
+  constructor (xo, name, poolIds, options) {
+    super(xo, name, poolIds, options)
+  }
+
+  _checkRessourcesThresholds (objects, averages) {
+    return filter(objects, object => {
+      const objectAverages = averages[object.id]
+
+      return (
+        objectAverages.cpu < this._thresholds.cpu.low ||
+        objectAverages.memoryFree > this._thresholds.memoryFree.low
+      )
+    })
+  }
+
+  async execute () {
+    throw new Error('Not implemented')
+
+    const hosts = this._getHosts()
+    const hostsStats = await this._getHostsStats(hosts, 'minutes')
+
+    // 1. Check if a ressource's utilization is under lower threshold.
+    const avgNow = computeRessourcesAverage(hosts, hostsStats, EXECUTION_DELAY)
+    let exceededHosts = this._checkRessourcesThresholds(hosts, avgNow, DENSITY_MODE)
+
+    // No ressource's utilization problem.
+    if (exceededHosts.length === 0) {
+      debug('No optimization found.')
+      return
+    }
+
+    // TODO
+  }
+}
+
 // ===================================================================
 // ===================================================================
 
@@ -479,22 +497,13 @@ class LoadBalancerPlugin {
 
     if (plans) {
       for (const plan of plans) {
-        const mode = plan.mode.performance
-          ? PERFORMANCE_MODE
-          : DENSITY_MODE
-
-        const { behavior: planBehavior } = plan
-        let behavior
-
-        if (planBehavior.low) {
-          behavior = LOW_BEHAVIOR
-        } else if (planBehavior.normal) {
-          behavior = NORMAL_BEHAVIOR
-        } else {
-          behavior = AGGRESSIVE_BEHAVIOR
-        }
-
-        this._addPlan({ name: plan.name, mode, behavior, poolIds: plan.pools })
+        this._addPlan({
+          name: plan.name,
+          mode: plan.mode.performance
+            ? PERFORMANCE_MODE
+            : DENSITY_MODE,
+          poolIds: plan.pools
+        })
       }
     }
 
@@ -511,15 +520,19 @@ class LoadBalancerPlugin {
     this._job.cron.stop()
   }
 
-  _addPlan (plan) {
-    const poolIds = plan.poolIds = uniq(plan.poolIds)
+  _addPlan ({ name, mode, poolIds }) {
+    poolIds = uniq(poolIds)
 
     // Check already used pools.
-    if (intersection(poolIds, this._poolIds) > 0) {
+    if (intersection(poolIds, this._poolIds).length > 0) {
       throw new Error(`Pool(s) already included in an other plan: ${poolIds}`)
     }
 
-    this._plans.push(new Plan(this.xo, plan))
+    this._poolIds = this._poolIds.concat(poolIds)
+    this._plans.push(mode === PERFORMANCE_MODE
+      ? new PerformancePlan(this.xo, name, poolIds)
+      : new DensityPlan(this.xo, name, poolIds)
+    )
   }
 
   _executePlans () {