pvcreate -vvvv /dev/md4 2&> laa

cat laa  | grep md4
#lvmcmdline.c:871         Processing: pvcreate -vvvv /dev/md4 2
#device/dev-cache.c:264         /dev/md4: Added to device cache
#filters/filter-sysfs.c:255         /dev/md4: Skipping (sysfs)
#filters/filter-persistent.c:274         /dev/md4: Skipping (cached)
#device/dev-cache.c:261         /dev/disk/by-id/md-uuid-c7883bd6:fb69bec8:b236ea3d:83ba9cb6: Aliased to /dev/md4 in device cache
#device/dev-cache.c:261         /dev/disk/by-uuid/c9c12c26-a317-4a13-9402-2f2e9a140e71: Aliased to /dev/md4 in device cache
#device/dev-cache.c:261         /dev/md/4: Aliased to /dev/md4 in device cache
#device/dev-cache.c:247         /dev/md4: Already in device cache
#filters/filter-sysfs.c:255         /dev/md4: Skipping (sysfs)
#pvcreate.c:84   Device /dev/md4 not found (or ignored by filtering).
#device/dev-cache.c:247         /dev/md4: Already in device cache