SLES 11 multipath issue

[S.M.Athar]

Salam All,
I am using HP DM Mulitpath with SLES 11 sp1. We are running 3 nodes cluster. We presented 5 vdisk to each host. On one host, multipath -ll command showing 4 disk instead of 5. but when I execute /sbin/multipathd the last disk also appears. Sometime the device id of this disk has also been changed then I have to restart multipath service and everything ok. It happen on every reboot in only one node.
Any friend have an idea why it is the behaviour. We are using HP Blades and EVa4400.
Regards
Athar