diff --git a/_constraints b/_constraints
index 2846a6a..a295ba1 100644
--- a/_constraints
+++ b/_constraints
@@ -9,6 +9,7 @@
       <size unit="G">60</size>
     </disk>
   </hardware>
+<!-- i586, armv6 and armv7 tend to run out of memory during builds -->
   <overwrite>
     <conditions>
       <arch>i586</arch>
@@ -25,6 +26,7 @@
       </disk>
     </hardware>
   </overwrite>
+<!-- x86_64 to use physical memory to speed builds up -->
   <overwrite>
     <conditions>
       <arch>x86_64</arch>
@@ -35,6 +37,7 @@
       </physicalmemory>
     </hardware>
   </overwrite>
+<!-- aarch64 is a time consuming build, try to use RAM -->
   <overwrite>
     <conditions>
       <arch>aarch64</arch>
@@ -48,6 +51,7 @@
       </disk>
     </hardware>
   </overwrite>
+<!-- 25GB of disk as 60GB is unavailable (and unrequired) on s390x and ppc64 -->
   <overwrite>
     <conditions>
       <arch>s390x</arch>