Hi, The reason is found out, as you've predicted. > is it because of slow read operation (i.e. some raid arrays are known to > wake-up slowly) The udev worker is blocked until timeout before killed, cause the "blkid" in /usr/lib/udev/rules.d/13-dm-disk.rules is too slow because of high IO load on the thin pool. After remove this rule: IMPORT{builtin}="blkid" for testing, the problem cannot be reproduced any more. But, we tried to increate udevd timeout to 5 min, the problem still happens; with 10 min timeout, can workaround this problem. >From my understanding, the blkid will only read the fs superblock, why it takes so long for a small IO to finish, even under high IO load? Regards, Eric _______________________________________________ linux-lvm mailing list linux-lvm@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/