The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform/tast-tests/+/3c21a6bb2ea85e9a51125c030a0d1f75d5f48b8a

commit 3c21a6bb2ea85e9a51125c030a0d1f75d5f48b8a
Author: Stephen Barber <smbarber@chromium.org>
Date: Thu Aug 23 14:37:04 2018

tast-tests: vm: switch to using raw disks

qcow2 performance is slow when extracting the container rootfs, so switch
to raw disks until performance improves.

BUG= chromium:876482 
TEST=strago boards no longer time out consistently

Change-Id: Iee0380ccf72e1f2162d88efc12b83213a4c74e14
Reviewed-on: https://chromium-review.googlesource.com/1184114
Commit-Ready: Stephen Barber <smbarber@chromium.org>
Tested-by: Stephen Barber <smbarber@chromium.org>
Reviewed-by: Dan Erat <derat@chromium.org>

[modify] https://crrev.com/3c21a6bb2ea85e9a51125c030a0d1f75d5f48b8a/src/chromiumos/tast/local/vm/concierge.go

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform/tast-tests/+/62d798f53e043f6052400afea16aa299ee2bbf05

commit 62d798f53e043f6052400afea16aa299ee2bbf05
Author: Jeffrey Kardatzke <jkardatzke@google.com>
Date: Thu Oct 18 21:54:31 2018

tast-tests: Use QCOW2 format for CrostiniStartEverything

There's an issue in the 3.18 kernel config that causes the RAW disk
format being used in this test to be orders of magnitude slower during
formatting than the QCOW2 format. This essentially undoes the gains we
get by using RAW disk format on the boards that need it most. For now we
will switch to QCOW2 format until we have the kernel changed to be more
optimal. (Although there is another open bug to switch back to QCOW2
after we make that format more optimal interestingly enough).

BUG= chromium:894521 , chromium:876482 
TEST=tast run vm.CrostiniStartEverything

Change-Id: I77c896260dc90dd53df317c59781dbfeee10328e
Reviewed-on: https://chromium-review.googlesource.com/1286277
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Jeffrey Kardatzke <jkardatzke@google.com>
Reviewed-by: Dan Erat <derat@chromium.org>
Reviewed-by: Stephen Barber <smbarber@chromium.org>

[modify] https://crrev.com/62d798f53e043f6052400afea16aa299ee2bbf05/src/chromiumos/tast/local/vm/concierge.go