Add leads for savings.

wiki/src/blueprint/hardware_for_automated_tests_take2.mdwn

@@ -67,3 +67,23 @@ Total   --- **$6200**
  * 1 x Supermicro SC113TQ-600W, 1U RM, WIO, 8x 2.5" SAS/SATA 600W       - $350
 
 Total   --- **$6650**
+
+## Ways to lower the price a bit
+
+No need to invest time into it immediately, but if we eventually decide
+to go this way and the total price is a bit too high, we should look
+into these options.
+
+### Less RAM
+
+Here, we pay for the test suite's temporary storage twice: once in RAM
+(disk cache managed by the kernel), once on disk. We could cut down on
+costs a bit by not buying all the corresponding RAM now, and instead
+relying purely on the SSDs (buy 128GB instead of 256GB for the new
+machine, which saves ~$1k).
+
+I'm curious what would be the performance hit if we did that. I guess
+it's easy enough to get a first very rough estimate (just give an
+isotesterN 10GB of RAM instead of 20GB, or something), but really it all
+depends on how the drives handle _multiple_ instances of the test suite
+writing/reading tons of data.