ASM的FAILGROUP

Normal 0 7.8 磅 0 2 false false false EN-US ZH-CN X-NONE以前一直以為NORMAL REDUNDANCY的話，FAILGROUP就是2，HIGH REDUNDANCY的話，FAILGROUP就是3

其實這是錯誤的，FAILGROUP是用於將磁碟分組，以保證丟失任何一組FAILGROUP磁碟，資料還是完整的

多用於多陣列，通過ASM來完成冗餘的環境。（EXTERNAL只能有一個FAILGROUP）

假設有4個陣列，每個陣列3塊盤，使用NORMAL REDUNDANCY建立DISKGROUP，4個FAILGROUP

CREATE DISKGROUP dgroup1 NORMAL REDUNDANCY

FAILGROUP controller1 DISK

'ORCL:ASM01', 'ORCL:ASM02', 'ORCL:ASM03'

FAILGROUP controller2 DISK

'ORCL:ASM04', 'ORCL:ASM05', 'ORCL:ASM06'

FAILGROUP controller3 DISK

'ORCL:ASM07', 'ORCL:ASM08', 'ORCL:ASM09'

FAILGROUP controller4 DISK

'ORCL:ASM10', 'ORCL:ASM11', 'ORCL:ASM12';

然後在上面建立一個1G的資料檔案

CREATE TABLESPACE asmtest DATAFILE '+DGROUP1' SIZE 1024M

然後看看資料的冗餘程度

SQL> SELECT COUNT(DISTINCT PXN_KFFXP),COUNT(DISTINCT XNUM_KFFXP)

2 FROM X$KFFXP

3 WHERE GROUP_KFFXP = 3

4 AND NUMBER_KFFXP =256

5 AND xnum_kffxp <> 2147483648;

COUNT(DISTINCTPXN_KFFXP) COUNT(DISTINCTXNUM_KFFXP)

------------------------ -------------------------

2050 1025

--資料檔案為1024M，加上一個BLOCK0，一共1025M，2個冗餘

SQL> SELECT COUNT(DISTINCT PXN_KFFXP),COUNT(DISTINCT XNUM_KFFXP)

2 FROM X$KFFXP

3 WHERE GROUP_KFFXP = 3

4 AND NUMBER_KFFXP =256

5 AND xnum_kffxp = 2147483648;

COUNT(DISTINCTPXN_KFFXP) COUNT(DISTINCTXNUM_KFFXP)

------------------------ -------------------------

3 1

--記錄塊分配的後設資料冗餘3份，其他後設資料也是冗餘3份

假設出現某個failgroup損壞

SQL> SELECT COUNT (DISTINCT xnum_kffxp)

2 FROM X$KFFXP a,v$asm_disk b

3 WHERE GROUP_KFFXP = 3

4 AND b.group_number=3

5 AND NUMBER_KFFXP =256

6 AND a.disk_kffxp = disk_number

7 AND b.failgroup <> 'CONTROLLER&i'

8 ;

Enter value for i: 1

old 7: AND b.failgroup <> 'CONTROLLER&i'

new 7: AND b.failgroup <> 'CONTROLLER1'

COUNT(DISTINCTXNUM_KFFXP)

-------------------------

1026

SQL> /

Enter value for i: 2

old 7: AND b.failgroup <> 'CONTROLLER&i'

new 7: AND b.failgroup <> 'CONTROLLER2'

COUNT(DISTINCTXNUM_KFFXP)

-------------------------

1026

SQL> /

Enter value for i: 3

old 7: AND b.failgroup <> 'CONTROLLER&i'

new 7: AND b.failgroup <> 'CONTROLLER3'

COUNT(DISTINCTXNUM_KFFXP)

-------------------------

1026

SQL> /

Enter value for i: 4

old 7: AND b.failgroup <> 'CONTROLLER&i'

new 7: AND b.failgroup <> 'CONTROLLER4'

COUNT(DISTINCTXNUM_KFFXP)

-------------------------

1026

其相關的1026個AU都是可訪問的

在看看後設資料，後設資料每個冗餘3份，任何一個FAILGROUP損壞，都能保證資料是完整的

SQL> SELECT NUMBER_KFFXP, XNUM_KFFXP, COUNT(*)

2 FROM X$KFFXP

3 WHERE GROUP_KFFXP = 3

4 AND NUMBER_KFFXP < 100

5 GROUP BY NUMBER_KFFXP, XNUM_KFFXP

6 ORDER BY 1, 2;

NUMBER_KFFXP XNUM_KFFXP COUNT(*)

------------ ---------- ----------

1 0 3

1 1 3

2 0 3

3 0 3

3 1 3

3 2 3

3 3 3

3 4 3

3 5 3

3 6 3

3 7 3

3 8 3

3 9 3

3 10 3

3 11 3

3 12 3

3 13 3

3 14 3

3 15 3

3 16 3

3 17 3

3 18 3

3 19 3

3 20 3

3 21 3

3 22 3

3 23 3

3 24 3

3 25 3

3 26 3

3 27 3

3 28 3

3 29 3

3 30 3

3 31 3

3 32 3

3 33 3

3 34 3

3 35 3

3 36 3

3 37 3

3 38 3

3 39 3

3 40 3

3 41 3

3 2147483648 3

4 0 3

4 1 3

5 0 3

6 0 3

50 rows selected.

SQL> SELECT COUNT(*)

2 FROM (SELECT DISTINCT NUMBER_KFFXP, XNUM_KFFXP

3 FROM X$KFFXP A, V$ASM_DISK B

4 WHERE GROUP_KFFXP = 3

5 AND B.GROUP_NUMBER = 3

6 AND NUMBER_KFFXP < 100

7 AND A.DISK_KFFXP = DISK_NUMBER

8 AND B.FAILGROUP <> 'CONTROLLER&i') ;

Enter value for i: 1

old 8: AND B.FAILGROUP <> 'CONTROLLER&i')

new 8: AND B.FAILGROUP <> 'CONTROLLER1')

COUNT(*)

----------

50

SQL> /

Enter value for i: 2

old 8: AND B.FAILGROUP <> 'CONTROLLER&i')

new 8: AND B.FAILGROUP <> 'CONTROLLER2')

COUNT(*)

----------

50

SQL> /

Enter value for i: 3

old 8: AND B.FAILGROUP <> 'CONTROLLER&i')

new 8: AND B.FAILGROUP <> 'CONTROLLER3')

COUNT(*)

----------

50

SQL> /

Enter value for i: 4

old 8: AND B.FAILGROUP <> 'CONTROLLER&i')

new 8: AND B.FAILGROUP <> 'CONTROLLER4')

COUNT(*)

----------

50

注意，預設建立的DISKGROUP，每個磁碟就是一個單獨的FAILGROUP

如上面的例子，4個陣列，在沒有指定failgroup的情況下，只要一組陣列出現了當機，資料就可能無法訪問，如果指定了failgroup，一組陣列損壞後，資料仍然能保證完整

在來看看冗餘報告:

SQL> SELECT NAME,

2 TYPE,

3 TOTAL_MB,

4 FREE_MB,

5 REQUIRED_MIRROR_FREE_MB,

6 USABLE_FILE_MB

7 FROM V$ASM_DISKGROUP

8 WHERE GROUP_NUMBER = 3;

NAME TYPE TOTAL_MB FREE_MB REQUIRED_MIRROR_FREE_MB USABLE_FILE_MB

---------- ------------ ---------- ---------- ----------------------- --------------

DGROUP1 NORMAL 12228 12054 3057 4498

如果failgroup失敗，那麼需要3057M的空間來恢復，大概3塊盤

如果是不指定failgroup建立DISKGROUP了？

CREATE DISKGROUP dgroup1 NORMAL REDUNDANCY DISK

'ORCL:ASM01', 'ORCL:ASM02', 'ORCL:ASM03', 'ORCL:ASM04', 'ORCL:ASM05', 'ORCL:ASM06',

'ORCL:ASM07', 'ORCL:ASM08', 'ORCL:ASM09', 'ORCL:ASM10', 'ORCL:ASM11', 'ORCL:ASM12';

SQL> /

NAME TYPE TOTAL_MB FREE_MB REQUIRED_MIRROR_FREE_MB USABLE_FILE_MB

---------- ------------ ---------- ---------- ----------------------- --------------

DGROUP1 NORMAL 12228 12057 1111 5473

如果不指定，只允許一個盤損壞，需要1111M來恢復，大概1塊盤

USABLE_FILE_MB 不代表能使用的磁碟限制，但當該列小於0時，不能正常DROP DISK，無法完成rebalance

來自 “ ITPUB部落格 ” ，連結：http://blog.itpub.net/8242091/viewspace-671590/，如需轉載，請註明出處，否則將追究法律責任。

ASM的FAILGROUP

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