On 17 March 2013 18:51, Paolo Bonzini <pbonz...@redhat.com> wrote: > Il 17/03/2013 01:04, Aurelien Jarno ha scritto: >> | boot | install build-dep | build lm-sensors | >> ------------------------+------+-------------------+------------------+ >> versatile | 1:09 | 2:27 | 4:09 | >> versatile cache=wb | 1:08 | 2:25 | 3:44 | > > Strange, cache=wb should be the default. > > The real problem with SD is that it doesn't have a flush command, hence > it cannot be made safe against power losses.
So, two things here: (a) the way to make it safe against power loss is that when the guest writes a block of data it has to really hit the emulated disk, because this is how the hardware works (b) I thought this was the reason cache=wb wasn't the default (ie that we weren't defaulting to 'may lose data on powerloss'). At the time I last looked into command line options for these boards I'm pretty sure it wasn't the default, because the performance improvement from turning on caching was huge. -- PMM
