#### 4.1 空间及磁盘路径 ``` sql --ASM磁盘组使用情况 used_percent, asm实例无法使用计算 col name format a15 set lines 200 with temp_asm as (select name,trunc(free_mb/1024,2) free_gb,trunc(total_mb/1024,2) total_gb,trunc(REQUIRED_MIRROR_FREE_MB/1024,2) req_free_gb,trunc(USABLE_FILE_MB/1024,2) uf_gb,type,state from v$asm_diskgroup) select * from ( select t.*,trunc((total_gb-free_gb)/total_gb*100,2) as used_percent from temp_asm t where type='EXTERN' union all select t.*,trunc(((total_gb-free_gb)/2)/((total_gb-req_free_gb)/2)*100,2) as used_percent from temp_asm t where type='NORMAL' union all select t.*,trunc(((total_gb-free_gb)/3)/((total_gb-req_free_gb)/3)*100,2) as used_percent from temp_asm t where type='HIGH') order by used_percent desc; --or select name,free_mb,total_mb,type,state from v$asm_diskgroup; --检查磁盘信息 set pages 999 col path format a20; col group_name format a15 col name format a20 col FAILGROUP_TYPE format a15 col FAILGROUP format a20 col state for a10 select a.group_number,b.name as group_name,a.FAILGROUP,a.name,a.path,a.state,a.total_mb from v$asm_disk a,v$asm_diskgroup b where a.group_number=b.group_number; ``` #### 4.2 磁盘修复检查 ``` #验证asm磁盘组 kfod asm_diskstring='/dev/mapper/*' disks=all kfed read /dev/mapper/data1 |grep grpname #asm 读取磁盘头 kfed read /dev/raw/raw2 text=/tmp/asmdisk_raw2.txt kfed read /dev/raw/raw2 aun=0 blkn=0 kfed read /dev/raw/raw2 blkn=510 > /tmp/1.txt kfed read /dev/raw/raw2 aun=1 blkn=254 #修复磁盘头 kfed write /dev/raw/raw2 aunum=0 blknum=0 text=/tmp/asmdisk_raw2.txt #or dd if=/dev/raw/raw2 of=/tmp/raw2.txt skip=510 bs=4096 count=1 dd if=/tmp/raw2.txt of=/dev/raw/raw2 ``` #### 4.3 ASM相关视图 View Name | X$ Table name | Description ---|---|--- V$ASM_DISKGROUP | X$KFGRP | performs disk discovery and lists diskgroups V$ASM_DISKGROUP_STAT | X$KFGRP_STAT | diskgroup stats without disk discovery V$ASM_DISK | X$KFDSK, X$KFKID | performs disk discovery, lists disks and their usage metrics V$ASM_DISK_STAT | X$KFDSK_STAT, X$KFKID | lists disks and their usage metrics V$ASM_FILE | X$KFFIL | lists ASM files, including metadata/asmdisk files V$ASM_ALIAS | X$KFALS | lists ASM aliases, files and directories V$ASM_TEMPLATE | X$KFTMTA | lists the available templates and their properties V$ASM_CLIENT | X$KFNCL | lists DB instances connected to ASM V$ASM_OPERATION | X$KFGMG | lists rebalancing operations N.A. | X$KFKLIB | available libraries, includes asmlib path N.A. | X$KFDPARTNER | lists disk-to-partner relationships N.A. | X$KFFXP | extent map table for all ASM files N.A. | X$KFDAT | extent list for all ASM disks N.A. | X$KFBH | describes the ASM cache (buffer cache of ASM in blocks of 4K (_asm_blksize) N.A. | X$KFCCE | a linked list of ASM blocks. to be further investigated #### 4.4 ASM内部视图X$KFFXP X$KFFXP是ASM(Automatic Storage Management)自动存储管理特性的重要内部视图，该视图反应了File Extent Map映射关系，ASM会将文件split成多个多个piece分片，这些分片被称为Extents。 在Disk上存放这些Extent的位置，就是我们常说的”Allocation Unit”。 KFF意为Kernel File，X$KFFXP即Kernel File Extent Maps， 该内部视图的一条记录代表一个Extent 字段含义如下： ``` GROUP_KFFXP diskgroup number (1 - 63) ASM disk group number. Join with v$asm_disk and v$asm_diskgroup NUMBER_KFFXP file number for the extent ASM file number. Join with v$asm_file and v$asm_alias COMPOUND_KFFXP (group_kffxp << 24) + file # File identifier. Join with compound_index in v$asm_file INCARN_KFFXP file incarnation number File incarnation id. Join with incarnation in v$asm_file PXN_KFFXP physical extent number Extent number per file XNUM_KFFXP extent number bit 31 set if indirect Logical extent number per file (mirrored extents have the same value) LXN_KFFXP logical extent number 0,1 used to identify primary/mirror extent, 2 identifies file header allocation unit (hypothesis) used in the query such that we go after only the primary extents, not secondary extents DISK_KFFXP disk on which AU is located Disk number where the extent is allocated. Join with v$asm_disk Relative position of the allocation unit from the beginning of the disk. AU_KFFXP AU number on disk of AU allocation unit size (1 MB) in v$asm_diskgroup #从11g开始加入了CHK_KFFXP SIZE_KFFXP 2个新的字段 CHK_KFFXP 未知 可能是范围为[0-256]的某种校验值 SIZE_KFFXP size_kffxp is used such that we account for variable sized extents. sum(size_kffxp) provides the number of AUs that are on that disk. ``` 在实例级别控制ASM Diskgroup AU 和 stripe size的是2个隐藏参数 _asm_ausize 1048576 以及 _asm_stripesize 131072。从11g开始一个Extent可能包含多个AU。 可以通过以下脚本查询文件与Extent等ASM属性的映射关系: ``` sql set linesize 140 pagesize 1400 col "FILE NAME" format a40 set head on select NAME "FILE NAME", NUMBER_KFFXP "FILE NUMBER", XNUM_KFFXP "EXTENT NUMBER", DISK_KFFXP "DISK NUMBER", AU_KFFXP "AU NUMBER", SIZE_KFFXP "NUMBER of AUs" from x$kffxp, v$asm_alias where GROUP_KFFXP = GROUP_NUMBER and NUMBER_KFFXP = FILE_NUMBER and system_created = 'Y' and lxn_kffxp = 0 order by name; ``` #### 4.5 条带化原理和rebalance ##### 条带化 ASM的条带化有两种：coarse和fine-gained 。AU是最小空间分配单元，缺省是1M，每个AU缺省由8个128K条带空间组成。 - 在coarse条带化中，一个磁盘对应一个AU 所以该条带化适合连续的I/O读写，比如全表扫描表 - 在fine-gained条带化里，一个AU中的8个128K条带空间，平均打散在磁盘上 也就是说，4个磁盘，1个AU是平均分布在4个磁盘，每个磁盘2个128K 适合于对数据读写延迟比较敏感的文件。如redo日志，控制文件，spfile等 ##### 重平衡 从diskgroup中添加或删除disk时候，将触发RBAL进程创建rebalance计划、计算时间开销.而后、发消息给ARBn进程（ASM Reblance）处理该请求 ARBn进程对每个extents进行locked, relocated和unlocked操作，执行过程中可以参考v$asm_operation视图. ARBn进程的数量由参数ASM_POWER_LIMIT决定, COD (Continuting Operation Directory)用于记录rebalances情况 如果rebalance失败，在重启instance时候，将从COD读取记录，重新启动rebalance 注意事项： - rebalance仅仅在diskgroup发生改变时候才进行的，并不是定时执行 如果rebalance执行过程中，server宕机，重启后会自动进行rebalance - 每个disk的大小必须是相同，如果存在一个小盘，因为rebalance将对每个盘的分配相同比例的空间，可能造成rebalance时候空间不足 如果执行过程中，空闲空间不足，造成rebalance失败，将出现ORA-15041错误，需要再添加disk 如果需要频繁添加disk，每一次都可能造成数据的频繁移动，为提高效率，最好批量添加 如果磁盘大小一样，仍然没有进行rebalance，需要查看asm_power_limit **参考** - https://www.askmaclean.com/archives/know-oracle-asm-basic-html.html - https://blog.csdn.net/iteye_4537/article/details/82130124