root@diomeda:/ # strace mdadm --create --verbose /dev/md1 --level=1 --raid-devices=2 /dev/sda1 /dev/sdb1
execve("/sbin/mdadm", ["mdadm", "--create", "--verbose", "/dev/md1", "--level=1", "--raid-devices=2", "/dev/sda1", "/dev/sdb1"], [/* 18 vars */]) = 0
brk(0)                                  = 0x806c000
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
mmap2(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f2a000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=46644, ...}) = 0
mmap2(NULL, 46644, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb7f1e000
close(3)                                = 0
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
open("/lib/libc.so.6", O_RDONLY)        = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0\20Z\1\000"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=6721115, ...}) = 0
mmap2(NULL, 1172860, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7dff000
mmap2(0xb7f17000, 16384, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x117) = 0xb7f17000
mmap2(0xb7f1b000, 9596, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb7f1b000
close(3)                                = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7dfe000
set_thread_area({entry_number:-1 -> 6, base_addr:0xb7dfe6b0, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 0
mprotect(0xb7f17000, 8192, PROT_READ)   = 0
munmap(0xb7f1e000, 46644)               = 0
time(NULL)                              = 1158408747
getpid()                                = 5451
brk(0)                                  = 0x806c000
brk(0x808d000)                          = 0x808d000
open("/dev/md1", O_RDWR)                = 3
fstat64(3, {st_mode=S_IFBLK|0660, st_rdev=makedev(9, 1), ...}) = 0
ioctl(3, 0x800c0910, 0xbfb3ebe8)        = 0
fstat64(3, {st_mode=S_IFBLK|0660, st_rdev=makedev(9, 1), ...}) = 0
ioctl(3, 0x800c0910, 0xbfb3ead8)        = 0
open("/dev/sda1", O_RDONLY|O_EXCL)      = -1 EBUSY (Device or resource busy)
write(2, "mdadm: Cannot open /dev/sda1: De"..., 54mdadm: Cannot open /dev/sda1: Device or resource busy
) = 54
open("/dev/sdb1", O_RDONLY|O_EXCL)      = -1 EBUSY (Device or resource busy)
write(2, "mdadm: Cannot open /dev/sdb1: De"..., 54mdadm: Cannot open /dev/sdb1: Device or resource busy
) = 54
write(2, "mdadm: create aborted\n", 22mdadm: create aborted
) = 22
exit_group(1)                           = ?
Process 5451 detached