Greenplum支持表空间，创建表空间时，需要指定filespace。

postgres=# \h create tablespace;

Command:     CREATE TABLESPACE

Description: define a new tablespace

Syntax:

CREATE TABLESPACE tablespace_name [OWNER username] FILESPACE filespace_name

那么什么是filespace呢？

GP在初始化完后，有一个默认的filespace ： pg_system。

表空间pg_default和pg_global都放在这个filespace下面。

也就是说一个filespace可以被多个表空间使用。

postgres=# select oid,* from pg_filespace;

oid  |  fsname   | fsowner

------+-----------+---------

3052 | pg_system |      10

(1 row)

postgres=# select * from pg_tablespace;

  spcname   | spcowner | spclocation | spcacl | spcprilocations | spcmirlocations | spcfsoid

------------+----------+-------------+--------+-----------------+-----------------+----------

pg_default |       10 |             |        |                 |                 |     3052

pg_global  |       10 |             |        |                 |                 |     3052

(2 rows)

还有TEMPORARY_FILES和TRANSACTION_FILES对应的filespace如下：

$gpfilespace --showtempfilespace

20151218:16:02:07:063949 gpfilespace:127.0.0.1:digoal-[INFO]:-

A tablespace requires a file system location to store its database

files. A filespace is a collection of file system locations for all components

in a Greenplum system (primary segment, mirror segment and master instances).

Once a filespace is created, it can be used by one or more tablespaces.

20151218:16:02:07:063949 gpfilespace:127.0.0.1:digoal-[INFO]:-Getting filespace information for TEMPORARY_FILES

20151218:16:02:08:063949 gpfilespace:127.0.0.1:digoal-[INFO]:-Checking for filespace consistency

20151218:16:02:08:063949 gpfilespace:127.0.0.1:digoal-[INFO]:-Obtaining current filespace entries used by TEMPORARY_FILES

20151218:16:02:09:063949 gpfilespace:127.0.0.1:digoal-[INFO]:-TEMPORARY_FILES OIDs are consistent for pg_system filespace

20151218:16:02:11:063949 gpfilespace:127.0.0.1:digoal-[INFO]:-TEMPORARY_FILES entries are consistent for pg_system filespace

20151218:16:02:11:063949 gpfilespace:127.0.0.1:digoal-[INFO]:-Obtaining current filespace entries used by TEMPORARY_FILES

20151218:16:02:11:063949 gpfilespace:127.0.0.1:digoal-[INFO]:-Current Filespace for TEMPORARY_FILES is pg_system

20151218:16:02:11:063949 gpfilespace:127.0.0.1:digoal-[INFO]:-1    /disk1/digoal/gpdata/gpseg-1

20151218:16:02:11:063949 gpfilespace:127.0.0.1:digoal-[INFO]:-25    /disk1/digoal/gpdata_mirror/gpseg0

20151218:16:02:11:063949 gpfilespace:127.0.0.1:digoal-[INFO]:-2    /disk1/digoal/gpdata/gpseg0

......

$gpfilespace --showtransfilespace

20151218:16:09:41:071104 gpfilespace:127.0.0.1:digoal-[INFO]:-

A tablespace requires a file system location to store its database

files. A filespace is a collection of file system locations for all components

in a Greenplum system (primary segment, mirror segment and master instances).

Once a filespace is created, it can be used by one or more tablespaces.

20151218:16:09:41:071104 gpfilespace:127.0.0.1:digoal-[INFO]:-Getting filespace information for TRANSACTION_FILES

20151218:16:09:41:071104 gpfilespace:127.0.0.1:digoal-[INFO]:-Checking for filespace consistency

20151218:16:09:41:071104 gpfilespace:127.0.0.1:digoal-[INFO]:-Obtaining current filespace entries used by TRANSACTION_FILES

20151218:16:09:42:071104 gpfilespace:127.0.0.1:digoal-[INFO]:-TRANSACTION_FILES OIDs are consistent for pg_system filespace

20151218:16:09:44:071104 gpfilespace:127.0.0.1:digoal-[INFO]:-TRANSACTION_FILES entries are consistent for pg_system filespace

20151218:16:09:44:071104 gpfilespace:127.0.0.1:digoal-[INFO]:-Obtaining current filespace entries used by TRANSACTION_FILES

20151218:16:09:44:071104 gpfilespace:127.0.0.1:digoal-[INFO]:-Current Filespace for TRANSACTION_FILES is pg_system

20151218:16:09:44:071104 gpfilespace:127.0.0.1:digoal-[INFO]:-1    /disk1/digoal/gpdata/gpseg-1

20151218:16:09:44:071104 gpfilespace:127.0.0.1:digoal-[INFO]:-25    /disk1/digoal/gpdata_mirror/gpseg0

20151218:16:09:44:071104 gpfilespace:127.0.0.1:digoal-[INFO]:-2    /disk1/digoal/gpdata/gpseg0

20151218:16:09:44:071104 gpfilespace:127.0.0.1:digoal-[INFO]:-26    /disk1/digoal/gpdata_mirror/gpseg1

......

如果我们的greenplum集群中，有SSD硬盘，又有SATA硬盘。怎样更好的利用这些空间呢？

方法1.

用flashcache或bcache，通过device mapper技术，将SSD和SATA绑定，做成块设备。

再通过 逻辑卷管理 或者 软RAID 或者 brtfs or zfs管理起来，做成大的文件系统。

（还有一种方法是用RHEL 7提供的LVM，可以将SSD作为二级缓存）

这种方法对GP来说，是混合动力，可以创建一个或多个文件系统（都具备混合动力）。

所以建议只需要一个pg_system filespace就够了(除非容量到了文件系统管理的极限，那样的话可以分成多个文件系统)。

用多个文件系统的情况下，就需要对每个文件系统，创建对应的目录，以及filespace。

方法2.

SSD和SATA分开，各自创建各自的文件系统。

对每个文件系统，创建对应的目录，以及filespace。

创建filespace非常简单，分几步。

如下：

1. 创建目录，需要在所有的角色对应的主机中创建。给予gp 操作系统管理用户对应的权限。

master

$ mkdir /ssd1/gpdata/master_p

$ chown gpadmin:gpadmin /ssd1/gpdata/master_p

master standby

$ mkdir /ssd1/gpdata/master_s

$ chown gpadmin:gpadmin /ssd1/gpdata/master_s

segment

$ mkdir /ssd1/gpdata_p

$ chown gpadmin:gpadmin /ssd1/gpdata_p

segment mirror

$ mkdir /ssd1/gpdata_s

$ chown gpadmin:gpadmin /ssd1/gpdata_s

2. 查看系统配置

postgres=# select dbid,content,role,preferred_role,hostname,port from gp_segment_configuration order by role,dbid;

dbid | content | role | preferred_role |     hostname      | port 

------+---------+------+----------------+-------------------+-------

    2 |       0 | m    | p              | digoal.sqa.zmf | 40000

    3 |       1 | m    | p              | digoal.sqa.zmf | 40001

    4 |       2 | m    | p              | digoal.sqa.zmf | 40002

    5 |       3 | m    | p              | digoal.sqa.zmf | 40003

    6 |       4 | m    | p              | digoal.sqa.zmf | 40004

    7 |       5 | m    | p              | digoal.sqa.zmf | 40005

    8 |       6 | m    | p              | digoal.sqa.zmf | 40006

    9 |       7 | m    | p              | digoal.sqa.zmf | 40007

   10 |       8 | m    | p              | digoal.sqa.zmf | 40008

   11 |       9 | m    | p              | digoal.sqa.zmf | 40009

   12 |      10 | m    | p              | digoal.sqa.zmf | 40010

   13 |      11 | m    | p              | digoal.sqa.zmf | 40011

   14 |      12 | m    | p              | digoal.sqa.zmf | 40012

   15 |      13 | m    | p              | digoal.sqa.zmf | 40013

   16 |      14 | m    | p              | digoal.sqa.zmf | 40014

   17 |      15 | m    | p              | digoal.sqa.zmf | 40015

   18 |      16 | m    | p              | digoal.sqa.zmf | 40016

   19 |      17 | m    | p              | digoal.sqa.zmf | 40017

   20 |      18 | m    | p              | digoal.sqa.zmf | 40018

   21 |      19 | m    | p              | digoal.sqa.zmf | 40019

   22 |      20 | m    | p              | digoal.sqa.zmf | 40020

   23 |      21 | m    | p              | digoal.sqa.zmf | 40021

   24 |      22 | m    | p              | digoal.sqa.zmf | 50011

    1 |      -1 | p    | p              | digoal.sqa.zmf |  1921

   25 |       0 | p    | m              | digoal.sqa.zmf | 41000

   26 |       1 | p    | m              | digoal.sqa.zmf | 41001

   27 |       2 | p    | m              | digoal.sqa.zmf | 41002

   28 |       3 | p    | m              | digoal.sqa.zmf | 41003

   29 |       4 | p    | m              | digoal.sqa.zmf | 41004

   30 |       5 | p    | m              | digoal.sqa.zmf | 41005

   31 |       6 | p    | m              | digoal.sqa.zmf | 41006

   32 |       7 | p    | m              | digoal.sqa.zmf | 41007

   33 |       8 | p    | m              | digoal.sqa.zmf | 41008

   34 |       9 | p    | m              | digoal.sqa.zmf | 41009

   35 |      10 | p    | m              | digoal.sqa.zmf | 41010

   36 |      11 | p    | m              | digoal.sqa.zmf | 41011

   37 |      12 | p    | m              | digoal.sqa.zmf | 41012

   38 |      13 | p    | m              | digoal.sqa.zmf | 41013

   39 |      14 | p    | m              | digoal.sqa.zmf | 41014

   40 |      15 | p    | m              | digoal.sqa.zmf | 41015

   41 |      16 | p    | m              | digoal.sqa.zmf | 41016

   42 |      17 | p    | m              | digoal.sqa.zmf | 41017

   43 |      18 | p    | m              | digoal.sqa.zmf | 41018

   44 |      19 | p    | m              | digoal.sqa.zmf | 41019

   45 |      20 | p    | m              | digoal.sqa.zmf | 41020

   46 |      21 | p    | m              | digoal.sqa.zmf | 41021

   47 |      22 | p    | m              | digoal.sqa.zmf | 41022

(47 rows)

3. 创建配置文件，格式如下，假如我要创建一个名为ssd1的filespace。

字段包含(hostname, dbid, DIR/$prefix + $content)

$ vi conf

filespace:ssd1

digoal.sqa.zmf:1:/ssd1/gpdata/master_p/gp-1

digoal.sqa.zmf:2:/ssd1/gpdata_p/gp0

digoal.sqa.zmf:3:/ssd1/gpdata_p/gp1

......

digoal.sqa.zmf:25:/ssd1/gpdata_s/gp0

digoal.sqa.zmf:26:/ssd1/gpdata_s/gp1

......

还有一种方法是使用gpfilespace -o conf来生成配置文件。(在提示时输入目录名DIR的部分即可)

4. 创建filespace

gpfilespace -c conf -h 127.0.0.1 -p 1921 -U digoal -W digoal

20151218:17:16:39:108364 gpfilespace:127.0.0.1:digoal-[INFO]:-Connecting to database

20151218:17:16:39:108364 gpfilespace:127.0.0.1:digoal-[INFO]:-Filespace "ssd1" successfully created

......

然后gpfilespace会自动在数据库执行以下DDL SQL。创建对应的filespace。

所以我们也可以自己在数据库中执行SQL来创建filespace。

CREATE FILESPACE ssd1

(

  1: '/disk1/digoal/new_p/gp-1',

  2: '/disk1/digoal/new_p/gp0',

  3: '/disk1/digoal/new_p/gp1',

  4: '/disk1/digoal/new_p/gp2',

  5: '/disk1/digoal/new_p/gp3',

  6: '/disk1/digoal/new_p/gp4',

  7: '/disk1/digoal/new_p/gp5',

  8: '/disk1/digoal/new_p/gp6',

  9: '/disk1/digoal/new_p/gp7',

  10: '/disk1/digoal/new_p/gp8',

  11: '/disk1/digoal/new_p/gp9',

  12: '/disk1/digoal/new_p/gp10',

  13: '/disk1/digoal/new_p/gp11',

  14: '/disk1/digoal/new_p/gp12',

  15: '/disk1/digoal/new_p/gp13',

  16: '/disk1/digoal/new_p/gp14',

  17: '/disk1/digoal/new_p/gp15',

  18: '/disk1/digoal/new_p/gp16',

  19: '/disk1/digoal/new_p/gp17',

  20: '/disk1/digoal/new_p/gp18',

  21: '/disk1/digoal/new_p/gp19',

  22: '/disk1/digoal/new_p/gp20',

  23: '/disk1/digoal/new_p/gp21',

  24: '/disk1/digoal/new_p/gp22',

  25: '/disk1/digoal/new_s/gp0',

  26: '/disk1/digoal/new_s/gp1',

  27: '/disk1/digoal/new_s/gp2',

  28: '/disk1/digoal/new_s/gp3',

  29: '/disk1/digoal/new_s/gp4',

  30: '/disk1/digoal/new_s/gp5',

  31: '/disk1/digoal/new_s/gp6',

  32: '/disk1/digoal/new_s/gp7',

  33: '/disk1/digoal/new_s/gp8',

  34: '/disk1/digoal/new_s/gp9',

  35: '/disk1/digoal/new_s/gp10',

  36: '/disk1/digoal/new_s/gp11',

  37: '/disk1/digoal/new_s/gp12',

  38: '/disk1/digoal/new_s/gp13',

  39: '/disk1/digoal/new_s/gp14',

  40: '/disk1/digoal/new_s/gp15',

  41: '/disk1/digoal/new_s/gp16',

  42: '/disk1/digoal/new_s/gp17',

  43: '/disk1/digoal/new_s/gp18',

  44: '/disk1/digoal/new_s/gp19',

  45: '/disk1/digoal/new_s/gp20',

  46: '/disk1/digoal/new_s/gp21',

  47: '/disk1/digoal/new_s/gp22'

);

现在你可以使用这个filespace了.

例如

1. 将temp , trans移动到这个新的filespace.

$gpfilespace --movetempfilespace ssd1

20151218:17:17:29:008363 gpfilespace:127.0.0.1:digoal-[INFO]:-

A tablespace requires a file system location to store its database

files. A filespace is a collection of file system locations for all components

in a Greenplum system (primary segment, mirror segment and master instances).

Once a filespace is created, it can be used by one or more tablespaces.

20151218:17:17:29:008363 gpfilespace:127.0.0.1:digoal-[INFO]:-Database was started in NORMAL mode

20151218:17:17:29:008363 gpfilespace:127.0.0.1:digoal-[INFO]:-Stopping Greenplum Database

20151218:17:17:57:008363 gpfilespace:127.0.0.1:digoal-[INFO]:-Starting Greenplum Database in master only mode

20151218:17:18:02:008363 gpfilespace:127.0.0.1:digoal-[INFO]:-Checking if filespace ssd1 exists

20151218:17:18:02:008363 gpfilespace:127.0.0.1:digoal-[INFO]:-Checking if filespace is same as current filespace

20151218:17:18:02:008363 gpfilespace:127.0.0.1:digoal-[INFO]:-Stopping Greenplum Database in master only mode

20151218:17:18:04:008363 gpfilespace:127.0.0.1:digoal-[INFO]:-Checking for connectivity

20151218:17:18:04:008363 gpfilespace:127.0.0.1:digoal-[INFO]:-Obtaining current filespace information

20151218:17:18:04:008363 gpfilespace:127.0.0.1:digoal-[INFO]:-Obtaining current filespace entries used by TEMPORARY_FILES

20151218:17:18:04:008363 gpfilespace:127.0.0.1:digoal-[INFO]:-Obtaining segment information ...

20151218:17:18:04:008363 gpfilespace:127.0.0.1:digoal-[INFO]:-Creating RemoteOperations list

20151218:17:18:04:008363 gpfilespace:127.0.0.1:digoal-[INFO]:-Moving TEMPORARY_FILES filespace from pg_system to ssd1 ...

20151218:17:18:06:008363 gpfilespace:127.0.0.1:digoal-[INFO]:-Starting Greenplum Database

$gpfilespace --movetransfilespace ssd1

...

20151218:17:19:17:055389 gpfilespace:127.0.0.1:digoal-[INFO]:-Moving TRANSACTION_FILES filespace from pg_system to ssd1 ...

20151218:17:21:16:055389 gpfilespace:127.0.0.1:digoal-[INFO]:-Starting Greenplum Database

2. 创建表空间，使用这个filespace.

postgres=# create tablespace tbs_ssd1 filespace ssd1;

CREATE TABLESPACE

postgres=# create table tt(id int) tablespace tbs_ssd1;

NOTICE:  Table doesn't have 'DISTRIBUTED BY' clause -- Using column named 'id' as the Greenplum Database data distribution key for this table.

HINT:  The 'DISTRIBUTED BY' clause determines the distribution of data. Make sure column(s) chosen are the optimal data distribution key to minimize skew.

CREATE TABLE

postgres=# select * from pg_tablespace ;

  spcname   | spcowner | spclocation | spcacl | spcprilocations | spcmirlocations | spcfsoid

------------+----------+-------------+--------+-----------------+-----------------+----------

pg_default |       10 |             |        |                 |                 |     3052

pg_global  |       10 |             |        |                 |                 |     3052

tbs_ssd1   |       10 |             |        |                 |                 |    69681

(3 rows)

postgres=# select * from pg_filespace;

  fsname   | fsowner

-----------+---------

pg_system |      10

ssd1      |      10

(2 rows)

greenplum为什么会引入filespace的概念？

因为主机目录结构可能不一样，所以原有的目录结构式的方法来创建表空间，可能不够灵活。

最后，如何查看每个节点的filespace和location的关系？

digoal=# select a.dbid,a.content,a.role,a.port,a.hostname,b.fsname,c.fselocation from gp_segment_configuration a,pg_filespace b,pg_filespace_entry c where a.dbid=c.fsedbid and b.oid=c.fsefsoid order by content;

dbid | content | role | port  |     hostname      |  fsname   |             fselocation             

------+---------+------+-------+-------------------+-----------+--------------------------------------

    1 |      -1 | p    |  1921 | digoal193096.zmf | pg_system | /data01/gpdata/master_pgdata/gpseg-1

    2 |       0 | p    | 40000 | digoal193096.zmf | pg_system | /data01/gpdata/gpseg0

    3 |       1 | p    | 40001 | digoal193096.zmf | pg_system | /data01/gpdata/gpseg1

    4 |       2 | p    | 40002 | digoal193096.zmf | pg_system | /data01/gpdata/gpseg2

    5 |       3 | p    | 40000 | digoal199092.zmf | pg_system | /data01/gpdata/gpseg3

    6 |       4 | p    | 40001 | digoal199092.zmf | pg_system | /data01/gpdata/gpseg4

    7 |       5 | p    | 40002 | digoal199092.zmf | pg_system | /data01/gpdata/gpseg5

    8 |       6 | p    | 40000 | digoal200164.zmf | pg_system | /data01/gpdata/gpseg6

    9 |       7 | p    | 40001 | digoal200164.zmf | pg_system | /data01/gpdata/gpseg7

   10 |       8 | p    | 40002 | digoal200164.zmf | pg_system | /data01/gpdata/gpseg8

   11 |       9 | p    | 40000 | digoal204016.zmf | pg_system | /data01/gpdata/gpseg9

   12 |      10 | p    | 40001 | digoal204016.zmf | pg_system | /data01/gpdata/gpseg10

   13 |      11 | p    | 40002 | digoal204016.zmf | pg_system | /data01/gpdata/gpseg11

   14 |      12 | p    | 40000 | digoal204063.zmf | pg_system | /data01/gpdata/gpseg12

   15 |      13 | p    | 40001 | digoal204063.zmf | pg_system | /data01/gpdata/gpseg13

   16 |      14 | p    | 40002 | digoal204063.zmf | pg_system | /data01/gpdata/gpseg14

   17 |      15 | p    | 40003 | digoal193096.zmf | pg_system | /data01/gpdata/gpseg15

   18 |      16 | p    | 40003 | digoal199092.zmf | pg_system | /data01/gpdata/gpseg16

   19 |      17 | p    | 40003 | digoal200164.zmf | pg_system | /data01/gpdata/gpseg17

   20 |      18 | p    | 40003 | digoal204016.zmf | pg_system | /data01/gpdata/gpseg18

   21 |      19 | p    | 40003 | digoal204063.zmf | pg_system | /data01/gpdata/gpseg19

   22 |      20 | p    | 40000 | digoal209198.zmf | pg_system | /data01/gpdata/gpseg22

   23 |      21 | p    | 40001 | digoal209198.zmf | pg_system | /data01/gpdata/gpseg23

   24 |      22 | p    | 40002 | digoal209198.zmf | pg_system | /data01/gpdata/gpseg24

   25 |      23 | p    | 40003 | digoal209198.zmf | pg_system | /data01/gpdata/gpseg25

(25 rows)