Problem with restart database

I've v7.0.0-1.How I can test ksafe?

select * from system
Look for current_fault_tolerance column, if it is 1 then your database is ksafe=1

Thanks! Can I take out the node from cluster and add the node  again?

If it's ksafe=1, yes you can take out the node. But before you go for removing and adding back the same node why don't you try to bring the down node from scratch. That means, from the down node rename the data and catalog folder. Go to one of the up node and run select make_ahm_now('true'). And then use the admintools to bring the down node up. Hope this helps. Try and let us know the result.

Thanks to your information, but I've had the ksafe test result:
select current_fault_tolerance  from system;
WARNING 4539:  Received no response from v_verticatest_node0001 in get cluster LGE
 current_fault_tolerance
-------------------------
                       0
(1 row)
Can I remove node from cluster?

can you show us the output of
select * from nodes and
select * from system;

Yes, I take out ip and node_id:
verticatest=> select node_name,node_state,catalog_path from nodes;       node_name        | node_state |                          catalog_path
------------------------+------------+-----------------------------------------------------------------
 v_verticatest_node0001 | DOWN       | /mnt/vertica/verticatest/v_verticatest_node0001_catalog/Catalog
 v_verticatest_node0002 | UP         | /mnt/vertica/verticatest/v_verticatest_node0002_catalog/Catalog
 v_verticatest_node0003 | UP         | /mnt/vertica/verticatest/v_verticatest_node0003_catalog/Catalog
(3 rows)
verticatest=> select * from system;WARNING 4539:  Received no response from v_verticatest_node0001 in get cluster LGE
 current_epoch | ahm_epoch | last_good_epoch | refresh_epoch | designed_fault_tolerance | node_count | node_down_count | current_fault_tolerance | catalog_revision_number | wos_used_bytes | wos_row_count | ros_used_bytes | ros_row_count | total_used_bytes | total_row_count
---------------+-----------+-----------------+---------------+--------------------------+------------+-----------------+-------------------------+-------------------------+----------------+---------------+----------------+---------------+------------------+-----------------
         56782 |     56780 |           56781 |            -1 |                        1 |          3 |               1 |                       0 |                  113867 |              0 |             0 |      375718735 |      38563730 |        375718735 |        38563730
(1 row)
May be I take out some fields from last query?

I think there are no relevant processes to be killed. Kindly start with step 2 onwards

Ok, thanks!