compute node1 and node 2 both use this backend and I can see only 1 compute services

[root@controller ~]# cinder service-list
+------------------+----------------+------+---------+-------+----------------------------+-----------------+
| Binary           | Host           | Zone | Status  | State | Updated_at                 | Disabled Reason |
+------------------+----------------+------+---------+-------+----------------------------+-----------------+
| cinder-scheduler | controller     | nova | enabled | up    | 2019-09-19T09:16:21.000000 | -               |
| cinder-volume    | FC@POWERMAX_FC | nova | enabled | up    | 2019-09-19T09:16:30.000000 | -               |
+------------------+----------------+------+---------+-------+----------------------------+-----------------+

You say that you can see only one compute service, but here you are listing Cinder services, not Nova services.

and now I am creating 5 instances from nova at same time (boot from volume) , the scheduler will report those error time to time like following ,but actually the 2 services on both 2 compute nodes runs fine ..

I guess that you are running cinder-volume on both compute nodes, and your problem is that only one of the cinder-volume services is up. Is that correct?

If I am guessing correctly, one of the two cinder-volume services is unable to reach cinder-api or is not running fine or not running at all. As a result, cinder-api is not aware of it and doesn't list it.

2019-09-19 17:53:10.951 20916 WARNING cinder.scheduler.host_manager [req-19e722e8-1523-4121-8987-3cb450a8038e 071294a19fa8463788822565e0927fce f43175c07dc8415899d6b350dbede772 - default default] volume service is down. (host: FC@POWERMAX_FC)

Where do you see this warning message? It looks like this particular service is not running fine.

If my guess is correct, I would expect to see additional information in the log of the problematic cinder-volume service.

Bernd.