Changing default root file system to btrfs

Paul Sokolovsky paul.sokolovsky at linaro.org
Thu Aug 4 13:17:11 UTC 2011


On Thu, 4 Aug 2011 12:46:58 +0100
James Tunnicliffe <james.tunnicliffe at 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...


-- 
Best Regards,
Paul

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