On Thu, 4 Aug 2011 12:46:58 +0100 James Tunnicliffe james.tunnicliffe@linaro.org wrote:
Hi,
Our current default root file system, ext3, is proving to be a bottleneck for SD card performance. Not only does it take a long time to format the partitions, but it also takes a long time to write to. This slows down creating images on SD cards a lot. I just did a very simple experiment running linaro-media-create, writing an Ubuntu Desktop image to an SD card:
ext3: 139.85user 35.27system 44:03.58elapsed 6%CPU (0avgtext+0avgdata 107360maxresident)k 2876115inputs+7048200outputs (958major+1677659minor)pagefaults 0swaps
btrfs: 146.52user 34.48system 19:57.16elapsed 15%CPU (0avgtext+0avgdata 107408maxresident)k 4417521inputs+6542992outputs (138major+1779874minor)pagefaults 0swaps
As I understand it, btrfs is considered OK for file systems running on systems that don't suffer from power failure, so for writing an image and testing it this should be fine.
So, what do people think about switching?
There were few concerns already expressed, so I just add: is btrfs supported out of the box by kernels in last ~3 Ubuntu releases? Because if one can't look at/change contents produced on an SD card, that undermines purpose of evaluation builds much.
Those ext3 vs btrfs results are very vivid though, but I wonder if it makes sense to try to tweak ext3 & mount options. And after all, we could prepare partition image(s) on the local HDD and dd them to a card...