greenplumn 建立索引失?。?No space left on device

一看錯誤提示感覺是空間不夠，其實不是。
5臺機器每臺20T的磁盤，每臺都有剩余8T。但是每次創(chuàng)建索引一天左右時間以后都會報錯。
錯誤日志如下：
2018-04-16 15:55:45.450606 CST,"gp","gp",p180444,th-2040876928,"192.168.1.8","25975",2018-04-15 14:23:56 CST,376948,con289,cmd1,seg31,,dx558714,x376948,sx1,"ERROR","53100","could not extend relation 1663/16384/21258: No space left on device",,"Check free disk space.",,,,"create index index_table_name_bitmap_package on table_name USING btree(package);",0,,"smgr.c",1335,"Stack trace:
1 0xae7486 postgres errstart (elog.c:503)
2 0x9ea06c postgres smgrextend (smgr.c:1329)
3 0x6db826 postgres <symbol not found> (nbtsort.c:338)
4 0x6dbc1a postgres <symbol not found> (nbtsort.c:602)
5 0x6dc7bf postgres _bt_leafbuild (nbtsort.c:838)
6 0x6d716a postgres btbuild (nbtree.c:146)
7 0xaef042 postgres OidFunctionCall3 (fmgr.c:1595)
8 0x76a270 postgres index_build (index.c:1451)
9 0x76afdd postgres index_create (index.c:967)
10 0x8037c6 postgres DefineIndex (indexcmds.c:731)
11 0x9f5bdb postgres ProcessUtility (utility.c:1312)
12 0x9f2123 postgres <symbol not found> (pquery.c:1521)
13 0x9f3836 postgres <symbol not found> (pquery.c:1631)
14 0x9f49d5 postgres PortalRun (pquery.c:1129)
15 0x67c16e postgres <symbol not found> (discriminator 13)
16 0x9f0386 postgres PostgresMain (postgres.c:4819)
17 0x99776e postgres <symbol not found> (postmaster.c:6672)
18 0x999400 postgres PostmasterMain (postmaster.c:1559)
19 0x8d286b postgres c_main (main.c:206)
20 0x7f53837aeb35 libc.so.6 __libc_start_main (??:0)
21 0x69dcc1 postgres <symbol not found> (??:?

我確定空間足夠，20T空間，5臺機器，每臺10表segment，然后創(chuàng)建索引前每臺剩余8T。有沒有知道原因？謝謝