oracle里的ols机制,Oracle ASM的AU（Allocation units）分配

Oracle ASM的AU(Allocation units)分配

SQL> select group_number,name,sector_size,block_size,allocation_unit_size from v$asm_diskgroup;

GROUP_NUMBER NAME   SECTOR_SIZE BLOCK_SIZE ALLOCATION_UNIT_SIZE

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

1 ARCHDG         512       4096              1048576

2 DATADG         512       4096              1048576在Oracle Database 11g中，可以通过类似如下语句在创建磁盘组时指定au_size:

SQL> CREATE DISKGROUP DATA DISK '/dev/raw/raw15', '/dev/raw/raw16',

'/dev/raw/raw17' ATTRIBUTE 'au_size' = '16M', 'compatible.asm' = '11.1' 'compatible.rdbms' = '11.1';ASM允许的相关参数可以从DB的实例中查询获得，以下是一系列和asm相关的初始化参数：

SQL> SELECT x.ksppinm NAME, y.ksppstvl VALUE, x.ksppdesc describ

2    FROM SYS.x$ksppi x, SYS.x$ksppcv y

3   WHERE x.indx = y.indx AND x.ksppinm LIKE '%&par%';

Enter value for par: asm

old   3:  WHERE x.indx = y.indx AND x.ksppinm LIKE '%&par%'

new   3:  WHERE x.indx = y.indx AND x.ksppinm LIKE '%asm%'

NAME                           VALUE                DESCRIB

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

asm_diskstring                                      disk set locations for discovery

_asm_disk_repair_time          14400                seconds to wait before dropping a failing disk

asm_diskgroups                                      disk groups to mount automatically

asm_power_limit                1                    number of processes for disk rebalancing

_asm_ausize                    1048576              allocation unit size

_asm_blksize                   4096                 metadata block size

_asm_acd_chunks                1                    initial ACD chunks created

_asm_libraries                 ufs                  library search order for discovery

_asm_maxio                     1048576              Maximum size of individual I/O request

_asm_allow_only_raw_disks      TRUE                 Discovery only raw devices

_asmlib_test                   0                    Osmlib test event

NAME                           VALUE                DESCRIB

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

_asm_allow_resilver_corruption FALSE                Enable disk resilvering for external redundancy

_asmsid                        asm                  ASM instance id

_asm_wait_time                 18                   Max/imum time to wait before asmb exits

_asm_stripewidth               8                    ASM file stripe width

_asm_stripesize                131072               ASM file stripe size

_asm_droptimeout               60                   timeout before offlined disks get dropped (in 3s ticks)

_asm_emulmax                   10000                max number of concurrent disks to emulate I/O errors

_asm_emultimeout               0                    timeout before emulation begins (in 3s ticks)

_asm_kfdpevent                 0                    KFDP event

20 rows selected.

By eygle on 2009-08-06 12:47 |

Comments (12) |

| 2359 |

12 Comments

没看清楚, 哪里可以查到 asm_stripesize?

The ASM coarse striping is always equal to the disk group AU size, but fine striping size always remains 128KB in any configuration.(11gR1 doc)

AU is ASM_disk's Unit,

Extent is ASM_File's Unit,

Strip is ASM_File's Strip.

但是怎么理解

_asm_stripewidth 8 ASM file stripe width

呢？

在Oracle 10gR2中，ASM AU的缺省单位大小是1M，相应的条带大小是128K。

在ASM中，可以通过调整_asm_ausize隐含参数的大小来进行调整，_asm_stripesize控制相应的条带化参数。

请问，ausize和stripesize，磁盘组中磁盘数目有什么关系？

_asm_ausize 和磁盘数目无关，用户可以根据数据文件的大小，磁盘组的大小来调整_asm_ausize设置，但是通常缺省设置是足够的。

如果使用外部磁盘阵列需要考虑stripesize和Raid基本块大小对齐么？

总结

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