On Sat, 27 Feb 2010 08:47:48 -0500 (EST) Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx> wrote: > Hello, > > I have two separate systems and with ext4 I cannot get speeds greater than > ~350MiB/s when using ext4 as the filesystem on top of a raid5 or raid0. > It appears to be a bug with ext4 (or its just that ext4 is slower for this > test)? > > Each system runs 2.6.33 x86_64. Could be related to the recent implementation of IO barriers in md. Can you try mounting your filesystem with -o barrier=0 and see how that changes the result. NeilBrown > > Can someone please confirm? > > Here is ext4: > > # dd if=/dev/zero of=bigfile bs=1M count=10240 > 10240+0 records in > 10240+0 records out > 10737418240 bytes (11 GB) copied, 29.8556 s, 360 MB/s > > The result is the same regardless of the RAID type (RAID-5 or RAID-0) > > Note, this is not a bandwidth problem: > > # dd if=/dev/zero of=/dev/md0 bs=1M count=10240 > 10240+0 records in > 10240+0 records out > 10737418240 bytes (11 GB) copied, 17.6871 s, 607 MB/s > > With XFS: > > p63:~# mkfs.xfs -f /dev/md0 > p63:~# mount /dev/md0 /r1 > p63:~# cd /r1 > 10240+0 records in > 10240+0 records out > 10737418240 bytes (11 GB) copied, 17.6078 s, 610 MB/s > > NOTE: With a HW raid controller (OR using XFS), I can get > 500 MiB/s, > this problem only occurs with SW raid (Linux/mdadm). > > Example (3ware 9650SE-16PML RAID-6, 15 drives (using EXT4) > $ dd if=/dev/zero of=bigfile bs=1M count=10240 > 10240+0 records in > 10240+0 records out > 10737418240 bytes (11 GB) copied, 21.1729 s, 507 MB/s > > Justin. > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
