diff --git a/share/man/onevm.1 b/share/man/onevm.1
index 5d6da7fc53..6903f85576 100644
--- a/share/man/onevm.1
+++ b/share/man/onevm.1
@@ -67,6 +67,8 @@
  \-\-cache cache_mode        Hypervisor cache mode: default, none,
                            writethrough, writeback, directsync or unsafe\.
                            (Only KVM driver)
+ \-\-discard discard_mode    Hypervisor discard mode: ignore or unmap\.
+                           (Only KVM driver)
  \-n, \-\-network id|name     Selects the virtual network
  \-i, \-\-ip ip               IP address for the new NIC
  \-l, \-\-list x,y,z          Selects columns to display with list command
@@ -370,7 +372,7 @@ disk\-attach \fIvmid\fR Attaches a disk to a running VM\. When using \-\-file ad
 .nf
 
 States: RUNNING
-valid options: file, image, target, cache
+valid options: file, image, target, cache, discard
 .
 .fi
 .
diff --git a/src/cli/onevm b/src/cli/onevm
index 3109a80b9a..c96bbb01e1 100755
--- a/src/cli/onevm
+++ b/src/cli/onevm
@@ -79,6 +79,14 @@ cmd=CommandParser::CmdParser.new(ARGV) do
             " writeback, directsync or unsafe. (Only KVM driver)"
     }
 
+    DISCARD={
+        :name => "discard",
+        :large => "--discard discard_mode",
+        :format => String,
+        :description => "Hypervisor discard mode: ignore or unmap."<<
+            " (Only KVM driver)"
+    }
+
     ENFORCE={
         :name  => "enforce",
         :short => "-e",
@@ -590,7 +598,7 @@ cmd=CommandParser::CmdParser.new(ARGV) do
 
     command :"disk-attach", disk_attach_desc, :vmid,
             :options => [OneVMHelper::FILE, OneVMHelper::IMAGE,
-                         TARGET, CACHE, PREFIX] do
+                         TARGET, CACHE, DISCARD, PREFIX] do
 
         if options[:file].nil? and options[:image].nil?
             STDERR.puts "Provide a template file or an image:"
@@ -618,6 +626,10 @@ cmd=CommandParser::CmdParser.new(ARGV) do
                 template<<", CACHE = \"#{options[:cache]}\""
             end
 
+            if options[:discard]
+                template<<", DISCARD = \"#{options[:discard]}\""
+            end
+
             template << " ]"
         end
 
diff --git a/src/sunstone/public/app/tabs/templates-tab/form-panels/create/wizard-tabs/storage/disk-tab/html.hbs b/src/sunstone/public/app/tabs/templates-tab/form-panels/create/wizard-tabs/storage/disk-tab/html.hbs
index 0ad0f8ac69..9300d24324 100644
--- a/src/sunstone/public/app/tabs/templates-tab/form-panels/create/wizard-tabs/storage/disk-tab/html.hbs
+++ b/src/sunstone/public/app/tabs/templates-tab/form-panels/create/wizard-tabs/storage/disk-tab/html.hbs
@@ -142,6 +142,17 @@
         <option value="native">{{tr "native"}}</option>
       </select>
     </div>
+    <div class="large-6 columns hypervisor only_kvm">
+      <label for="DISCARD">
+        {{tr "DISCARD"}}
+        <span class="tip">{{tr "Set DISCARD feature."}}</span>
+      </label>
+      <select wizard_field="DISCARD" id="DISCARD" name="DISCARD">
+        <option value=""></option>
+        <option value="ignore">{{tr "ignore"}}</option>
+        <option value="unmap">{{tr "unmap"}}</option>
+      </select>
+    </div>
     <div class="large-6 columns hypervisor only_kvm">
       <label for="TOTAL_BYTES_SEC">
         {{tr "Total Bytes Sec"}}
diff --git a/src/vmm/LibVirtDriverKVM.cc b/src/vmm/LibVirtDriverKVM.cc
index 661652e9ab..aa0af1e788 100644
--- a/src/vmm/LibVirtDriverKVM.cc
+++ b/src/vmm/LibVirtDriverKVM.cc
@@ -119,6 +119,7 @@ int LibVirtDriver::deployment_description_kvm(
     string  driver          = "";
     string  cache           = "";
     string  disk_io         = "";
+    string  discard         = "";
     string  source          = "";
     string  clone           = "";
     string  ceph_host       = "";
@@ -146,6 +147,7 @@ int LibVirtDriver::deployment_description_kvm(
     string  default_driver          = "";
     string  default_driver_cache    = "";
     string  default_driver_disk_io  = "";
+    string  default_driver_discard  = "";
     bool    readonly;
 
     const VectorAttribute * nic;
@@ -408,6 +410,9 @@ int LibVirtDriver::deployment_description_kvm(
 
     get_default("DISK", "IO", default_driver_disk_io);
 
+    get_default("DISK", "DISCARD", default_driver_discard);
+
+
     get_default("DISK", "TOTAL_BYTES_SEC", default_total_bytes_sec);
     get_default("DISK", "READ_BYTES_SEC", default_read_bytes_sec);
     get_default("DISK", "WRITE_BYTES_SEC", default_write_bytes_sec);
@@ -434,6 +439,7 @@ int LibVirtDriver::deployment_description_kvm(
         driver          = disk->vector_value("DRIVER");
         cache           = disk->vector_value("CACHE");
         disk_io         = disk->vector_value("IO");
+        discard         = disk->vector_value("DISCARD");
         source          = disk->vector_value("SOURCE");
         clone           = disk->vector_value("CLONE");
 
@@ -645,6 +651,20 @@ int LibVirtDriver::deployment_description_kvm(
             file << " io='" << default_driver_disk_io << "'";
         }
 
+       if ( !discard.empty() || !default_driver_discard.empty() )
+       {
+            file << "' discard='";
+
+            if ( !discard.empty() )
+            {
+                file << discard << "'";
+            }
+            else
+            {
+                file << default_driver_discard << "'";
+            }
+        }
+
         file << "/>" << endl;
 
         // ---- I/O Options  ----
diff --git a/src/vmm_mad/exec/vmm_exec_kvm.conf b/src/vmm_mad/exec/vmm_exec_kvm.conf
index 97f3f21b16..f30b107179 100644
--- a/src/vmm_mad/exec/vmm_exec_kvm.conf
+++ b/src/vmm_mad/exec/vmm_exec_kvm.conf
@@ -21,7 +21,7 @@
 #  - os [kernel,initrd,boot,root,kernel_cmd,arch,machine]
 #  - vcpu
 #  - features [acpi, pae, apic, hyperv, localtime]
-#  - disk [driver, cache, io, total_bytes_sec, total_iops_sec, read_bytes_sec, write_bytes_sec, read_iops_sec, write_iops_sec]
+#  - disk [driver, cache, io, discard, total_bytes_sec, total_iops_sec, read_bytes_sec, write_bytes_sec, read_iops_sec, write_iops_sec]
 #  - nic  [filter, model]
 #  - raw
 #  - hyperv_options: options used for FEATURES = [ HYPERV = yes ]
diff --git a/src/vmm_mad/remotes/kvm/attach_disk b/src/vmm_mad/remotes/kvm/attach_disk
index 68919cb6fc..1b01d12bc8 100755
--- a/src/vmm_mad/remotes/kvm/attach_disk
+++ b/src/vmm_mad/remotes/kvm/attach_disk
@@ -44,6 +44,7 @@ done < <($XPATH     /VMM_DRIVER_ACTION_DATA/VM/ID \
                     $DISK_XPATH/TYPE \
                     $DISK_XPATH/READONLY \
                     $DISK_XPATH/CACHE \
+                    $DISK_XPATH/DISCARD \
                     $DISK_XPATH/SOURCE \
                     $DISK_XPATH/DISK_ID \
                     $DISK_XPATH/CLONE \
@@ -56,6 +57,7 @@ DRIVER="${XPATH_ELEMENTS[j++]:-$DEFAULT_TYPE}"
 TYPE="${XPATH_ELEMENTS[j++]}"
 READONLY="${XPATH_ELEMENTS[j++]}"
 CACHE="${XPATH_ELEMENTS[j++]}"
+DISCARD="${XPATH_ELEMENTS[j++]}"
 IMG_SRC="${XPATH_ELEMENTS[j++]}"
 DISK_ID="${XPATH_ELEMENTS[j++]}"
 CLONE="${XPATH_ELEMENTS[j++]}"
@@ -127,6 +129,10 @@ esac
     CACHE="$DEFAULT_ATTACH_CACHE"
 [ -n "$CACHE" ] && CACHE="cache='$CACHE'"
 
+[ -z "$DISCARD" ] && [ -n "$DEFAULT_ATTACH_DISCARD" ] && \
+    DISCARD="$DEFAULT_ATTACH_DISCARD"
+[ -n "$DISCARD" ] && DISCARD="discard='$DISCARD'"
+
 if [ "$READONLY" = "YES" ]; then
     READONLY="<readonly/>"
 else
@@ -135,7 +141,7 @@ fi
 
 cat <<EOF > $ATTACH_FILE
 <disk type='$TYPE_XML' device='$DEVICE'>
-  <driver name='qemu' type='$DRIVER' $CACHE/>
+  <driver name='qemu' type='$DRIVER' $CACHE $DISCARD/>
   <source $TYPE_SOURCE='$SOURCE' $SOURCE_ARGS>
   $SOURCE_HOST
   </source>
diff --git a/src/vmm_mad/remotes/kvm/kvmrc b/src/vmm_mad/remotes/kvm/kvmrc
index b09ddf037c..25d88e2cdb 100644
--- a/src/vmm_mad/remotes/kvm/kvmrc
+++ b/src/vmm_mad/remotes/kvm/kvmrc
@@ -36,4 +36,12 @@ export SHUTDOWN_TIMEOUT=300
 #DEFAULT_ATTACH_CACHE=none
 
 # Uncomment this line to set options for the virsh migrate command
-#MIGRATE_OPTIONS=--unsafe
\ No newline at end of file
+#MIGRATE_OPTIONS=--unsafe
+
+# IDE and SCSI disks always have the ability to issue "discard"
+# (aka TRIM or UNMAP) commands. However, by default "discard" commands are
+# silently ignored as they can cause performance degradation and fragmentation.
+# To enable them, the "-drive" option now supports a "discard" suboption; the
+# default value is "ignore" (or its synonym "off"), and the other valid value
+# is "unmap" (or "on").
+#DEFAULT_ATTACH_DISCARD=unmap