当在使用greenplum过程中有不当的操作时，可能会出现segment节点宕掉的情况（比如在greenplum运行的过程中停掉其中几台segment节点的服务器），通过下面的方法可以恢复segment。
下面是现场出现的故障情况：
[gpadmin@tj-soc-c04-csfb1 ~]$ gpstate -m
20161010:16:35:54:026100 gpstate:tj-soc-c04-csfb1:gpadmin-[INFO]:-Starting gpstate with args: -m
20161010:16:35:55:026100 gpstate:tj-soc-c04-csfb1:gpadmin-[INFO]:-local Greenplum Version: 'postgres (Greenplum Database) 4.3.6.2 build 1'
20161010:16:35:55:026100 gpstate:tj-soc-c04-csfb1:gpadmin-[INFO]:-master Greenplum Version: 'PostgreSQL 8.2.15 (Greenplum Database 4.3.6.2 build 1) on x86_64-unknown-linux-gnu, compiled by GCC gcc (GCC) 4.4.2 compiled on Nov 12 2015 23:50:28'
20161010:16:35:55:026100 gpstate:tj-soc-c04-csfb1:gpadmin-[INFO]:-Obtaining Segment details from master...
20161010:16:35:55:026100 gpstate:tj-soc-c04-csfb1:gpadmin-[INFO]:--------------------------------------------------------------
20161010:16:35:55:026100 gpstate:tj-soc-c04-csfb1:gpadmin-[INFO]:--Current GPDB mirror list and status
20161010:16:35:55:026100 gpstate:tj-soc-c04-csfb1:gpadmin-[INFO]:--Type = Group
20161010:16:35:55:026100 gpstate:tj-soc-c04-csfb1:gpadmin-[INFO]:--------------------------------------------------------------
20161010:16:35:55:026100 gpstate:tj-soc-c04-csfb1:gpadmin-[INFO]:- Mirror Datadir Port Status Data Status
20161010:16:35:55:026100 gpstate:tj-soc-c04-csfb1:gpadmin-[WARNING]:-tj-soc-c04-csfb2 /data1/gpdata/mirror/gpseg0 41000 Failed <<<<<<<<
20161010:16:35:55:026100 gpstate:tj-soc-c04-csfb1:gpadmin-[WARNING]:-tj-soc-c04-csfb2 /data1/gpdata/mirror/gpseg1 41001 Failed <<<<<<<<
20161010:16:35:55:026100 gpstate:tj-soc-c04-csfb1:gpadmin-[WARNING]:-tj-soc-c04-csfb3 /data1/gpdata/mirror/gpseg2 41000 Failed <<<<<<<<
20161010:16:35:55:026100 gpstate:tj-soc-c04-csfb1:gpadmin-[WARNING]:-tj-soc-c04-csfb3 /data1/gpdata/mirror/gpseg3 41001 Failed <<<<<<<<
20161010:16:35:55:026100 gpstate:tj-soc-c04-csfb1:gpadmin-[INFO]:- tj-soc-c04-csfb4 /data1/gpdata/mirror/gpseg4 41000 Acting as Primary Change Tracking
20161010:16:35:55:026100 gpstate:tj-soc-c04-csfb1:gpadmin-[INFO]:- tj-soc-c04-csfb4 /data1/gpdata/mirror/gpseg5 41001 Acting as Primary Change Tracking
20161010:16:35:55:026100 gpstate:tj-soc-c04-csfb1:gpadmin-[WARNING]:-tj-soc-c04-csfb1 /data1/gpdata/mirror/gpseg6 41000 Failed <<<<<<<<
20161010:16:35:55:026100 gpstate:tj-soc-c04-csfb1:gpadmin-[WARNING]:-tj-soc-c04-csfb1 /data1/gpdata/mirror/gpseg7 41001 Failed <<<<<<<<
20161010:16:35:55:026100 gpstate:tj-soc-c04-csfb1:gpadmin-[INFO]:--------------------------------------------------------------
20161010:16:35:55:026100 gpstate:tj-soc-c04-csfb1:gpadmin-[WARNING]:-2 segment(s) configured as mirror(s) are acting as primaries
20161010:16:35:55:026100 gpstate:tj-soc-c04-csfb1:gpadmin-[WARNING]:-6 segment(s) configured as mirror(s) have failed
20161010:16:35:55:026100 gpstate:tj-soc-c04-csfb1:gpadmin-[WARNING]:-2 mirror segment(s) acting as primaries are in change tracking
可以看到有6个节点Failed，有2个节点的Primary和Mirror交换了。
一、首先需要停掉GP
gpstop -M fast -a 这样会告诉你有几个节点DOWN了
二、启动GP
gpstart 启动数据库会忽略DOWN的节点
三、生成一个恢复配置文件
gprecoverseg -o ./recov 会在当前目录生成一个recov文件，里面包含了要恢复的节点信息
recov文件内容如下：（注意：这个文件不是手动创建的，而是通过gprecoverseg -o ./recov命令生成的
filespaceOrder=
tj-soc-c04-csfb2:41000:/data1/gpdata/mirror/gpseg0
tj-soc-c04-csfb2:41001:/data1/gpdata/mirror/gpseg1
tj-soc-c04-csfb3:41000:/data1/gpdata/mirror/gpseg2
tj-soc-c04-csfb3:41001:/data1/gpdata/mirror/gpseg3
tj-soc-c04-csfb1:41000:/data1/gpdata/mirror/gpseg6
tj-soc-c04-csfb1:41001:/data1/gpdata/mirror/gpseg7
四、使用恢复配置文件恢复节点
$gprecoverseg -i ./recov
恢复过程中可以用gpstate -m 查看恢复状态：Resynchronizing（表示正在恢复中），Synchronized（表示恢复完毕）
五、调整Primary和Mirror
上面的情况中有Primary和Mirror兑换的情况，所以需要把他们换回来，可以用下面的命令
gprecoverseg -r
等待所有的节点都是Synchronized后，segment就恢复好了