On 17 August 2011 08:55, Tixy tixy@clara.net wrote:
On Wed, 2011-08-17 at 00:13 -0300, Ricardo Salveti wrote:
Yeah, if we're doing this change it seems it would make more sense to jump directly to the btrfs, unless we can demonstrate that the performance is not that superior and have any kind of blocker issues.
Do we have any kind of benchmark results comparing each filesystem when using them with SD cards around?
I'm doing some benchmarking, though it's mostly being aimed at producing media access patterns to feed into a simulation tool. From these access patterns, btrfs looks a lot worse than any ext file system.
I just looked at the timestamps of my blktrace logs to get some real world timings. For untaring kernel source on one of my good performance SD cards on a Beagleboard-xM takes:
m s ext4 3:30 ext3 8:30 ext2 5:00 btrfs 13:40 nilfs 10:40 logfs 10:00
this is using default mount options for file system but with noatime.
These timings also bear out preliminary results from my simulation code. Which I'm glad of :-)
This is odd. When I performed tests btrfs and ext4 were both about the same speed for copying a mixture of large and small files to. I was testing them using my laptop card reader though. Tixy: Do you get similar btrfs vs ext4 results using the same card on an x86 host? Is your host 64 or 32 bit? I can't find any warnings about btrfs being slow on 32 bit systems during a quick search, but ZFS certainly works better on 64 bit systems. Perhaps btrfs is more optimal on 64 bit systems as well.
One thing I noticed during Ubuntu boot on my Panda was that the mount process would say that it detected btrfs was running on a flash card and it had enabled flash mode. I don't know what is different in flash mode and I don't know if when I let Ubuntu auto-mount a flash card for testing on my Laptop if it enabled it. The only mount option I can find that sounds right is "ssd", which isn't on when I just tested it now.