This hangs on x64 centos linux 6.5 4gb ram, 2gb swap, 3ware raid card 9650se-4lpml

log from kernel messages

INFO: task sadc:1716 blocked for more than 120 seconds.
Not tainted 2.6.32-431.el6.x86_64 #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
sadc D 0000000000000000 0 1716 1715 0x00000084
ffff8800379afdc8 0000000000000086 ffff8800379afd90 ffff8800379afd8c
ffff8800379afd88 ffff88011fc23280 ffff880028216840 0000000000000400
ffff880119c83058 ffff8800379affd8 000000000000fbc8 ffff880119c83058
Call Trace:
[] ? prepare_to_wait+0x4e/0x80
[] jbd2_log_wait_commit+0xc5/0x140 [jbd2]
[] ? autoremove_wake_function+0x0/0x40
[] ? do_writepages+0x21/0x40
[] jbd2_complete_transaction+0x68/0xb0 [jbd2]
[] ext4_sync_file+0x121/0x1d0 [ext4]
[] vfs_fsync_range+0xa1/0x100
[] vfs_fsync+0x1d/0x20
[] do_fsync+0x3e/0x60
[] sys_fdatasync+0x13/0x20
[] system_call_fastpath+0x16/0x1b
INFO: task sadc:1716 blocked for more than 120 seconds.
Not tainted 2.6.32-431.el6.x86_64 #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
sadc D 0000000000000000 0 1716 1715 0x00000084
ffff8800379afdc8 0000000000000086 ffff8800379afd90 ffff8800379afd8c
ffff8800379afd88 ffff88011fc23280 ffff880028216840 0000000000000400
ffff880119c83058 ffff8800379affd8 000000000000fbc8 ffff880119c83058
Call Trace:
[] ? prepare_to_wait+0x4e/0x80
[] jbd2_log_wait_commit+0xc5/0x140 [jbd2]
[] ? autoremove_wake_function+0x0/0x40
[] ? do_writepages+0x21/0x40
[] jbd2_complete_transaction+0x68/0xb0 [jbd2]
[] ext4_sync_file+0x121/0x1d0 [ext4]
[] vfs_fsync_range+0xa1/0x100
[] vfs_fsync+0x1d/0x20
[] do_fsync+0x3e/0x60
[] sys_fdatasync+0x13/0x20
[] system_call_fastpath+0x16/0x1b


change the default value of vm.dirty_ratio and vm.dirty_background_ratio kernel parameters


vim /etc/sysctl.conf
vm.dirty_ratio = 5
vm.dirty_background_ratio = 5

sysctl -p