I found this article on the web at
http://comments.gmane.org/gmane.linux.file-systems.zfs.user/22288
It worked for me. I now have my zpool back online
Re: CentOS: Failed to load ZFS module stack
Might have something to do with old kernel-devel packages and whatnot, I take it you recently updated to
CentOS 7.1 recently? Try this;
#### Now remove all references to 0.6.3 - since your install looks broken already, this may not work/error out.
dkms remove --all zfs/0.6.3
dkms remove --all spl/0.6.3
#### Now remove all traces of ZoL, second via any remaining zfs kernel modules
find /lib/modules/$(uname -r)/extra -name "splat.ko" -or -name "zcommon.ko" -or -name "zpios.ko" -or -name "spl.ko" -or -name "zavl.ko" -or -name "zfs.ko" -or -name "znvpair.ko" -or -name "zunicode.ko" | xargs rm -f
find /lib/modules/$(uname -r)/weak-updates/ -name "splat.ko" -or -name "zcommon.ko" -or -name "zpios.ko" -or -name "spl.ko" -or -name "zavl.ko" -or -name "zfs.ko" -or -name "znvpair.ko" -or -name "zunicode.ko" | xargs rm -f
#### Now get a list of all installed kernel and related RPMs
rpm -qa | grep kernel
#### Now erase all kernel headers and etc that are older than your current kernel. Below are examples
assuming you updated from CentOS 7.0 to 7.1 **DO NOT COPY PASTE THIS LINE, PAY CLOSE ATTENTION TO RESULTS OF
LAST COMMAND AND COMMON SENSE**
yum erase kernel-3.10.0-123.13.2.el7.x86_64 kernel-devel-3.10.0-123.13.2.el7.x86_64
#### Now remove all current kernel headers and tools - **this is probably not needed and overkill**
yum erase kernel-headers kernel-devel kernel-tools
#### Now remove all traces of ZoL, first via yum
yum erase zfs zfs-dkms libzfs2 spl spl-dkms dkmsc
#### After all this try installing ZFS again.
