Oracle ASM Rebalance执行过程

2017-01-12 09:52:41来源:作者:Java & Oracle人点击

磁盘组的rebalance什么时候能完成?这没有一个具体的数值,但ASM本身已经给你提供了一个估算值(GV$ASM_OPERATION.EST_MINUTES),想知道rebalance完成的精确的时间,虽然不能给出一个精确的时间,但是可以查看一些rebalance的操作细节,让你知道当前rebalance是否正在进行中,进行到哪个阶段,以及这个阶段是否需要引起你的关注。

理解rebalance

rebalance操作本身包含了3个阶段-planning, extents relocation 和 compacting,就rebalance需要的总时间而言,planning阶段需要的时间是非常少的,你通常都不用去关注这一个阶段,第二个阶段extent relocation一般会占取rebalance阶段的大部分时间,也是我们最为需要关注的阶段,最后我们也会讲述第三阶段compacting阶段在做些什么。

首先需要明白为什么会需要做rebalance,如果你为了增加磁盘组的可用空间,增加了一块新磁盘或者为了调整磁盘的空间,例如resizing或者删除磁盘,你可能也不会太去关注rebalance啥时候完成。但是,如果磁盘组中的一块磁盘损坏了,这个时候你就有足够的理由关注rebalance的进度了,假如,你的磁盘组是normal冗余的,这个时候万一你损坏磁盘的partner磁盘也损坏,那么你的整个磁盘组会被dismount,所有跑在这个磁盘组上的数据库都会crash,你可能还会丢失数据。在这种情况下,你非常需要知道rebalance什么时候完成,实际上,你需要知道第二个阶段extent relocation什么时候完成,一旦它完成了,整个磁盘组的冗余就已经完成了(第三个阶段对于冗余度来说并不重要,后面会介绍)。

Extents relocation

为了进一步观察extents relocation阶段,我删除了具有默认并行度的磁盘组上的一块磁盘:

SQL> show parameter powerNAME TYPE VALUE------------------------------------ ---------------------- ------------------------------asm_power_limit integer 114:47:35 SQL> select group_number,disk_number,name,state,path,header_status from v$asm_disk where group_number=5;GROUP_NUMBER DISK_NUMBER NAME STATE PATH HEADER_STATUS------------ ----------- -------------------- -------------------- -------------------- -------------------- 5 0 TESTDG_0000 NORMAL /dev/raw/raw7 MEMBER 5 2 TESTDG_0002 NORMAL /dev/raw/raw13 MEMBER 5 1 TESTDG_0001 NORMAL /dev/raw/raw12 MEMBER 5 3 TESTDG_0003 NORMAL /dev/raw/raw14 MEMBER14:48:38 SQL> alter diskgroup testdg drop disk TESTDG_0000;Diskgroup altered.

下面视图GV$ASMOPERATION的ESTMINUTES字段给出了估算值的时间,单位为分钟,这里给出的估算时间为9分钟。

14:49:04 SQL> select inst_id, operation, state, power, sofar, est_work, est_rate, est_minutes from gv$asm_operation where group_number=5; INST_ID OPERATION STATE POWER SOFAR EST_WORK EST_RATE EST_MINUTES---------- -------------------- -------------------- ---------- ---------- ---------- ---------- ----------- 1 REBAL RUN 1 4 4748 475 9

大约过了1分钟后,EST_MINUTES的值变为了0分钟:

14:50:22 SQL> select inst_id, operation, state, power, sofar, est_work, est_rate, est_minutes from gv$asm_operation where group_number=5; INST_ID OPERATION STATE POWER SOFAR EST_WORK EST_RATE EST_MINUTES---------- -------------------- -------------------- ---------- ---------- ---------- ---------- ----------- 1 REBAL RUN 1 3030 4748 2429 0

有些时候EST_MINUTES的值可能并不能给你太多的证据,我们还可以看到SOFAR(截止目前移动的UA数)的值一直在增加,恩,不错,这是一个很好的一个观察指标。ASM的alert日志中也显示了删除磁盘的操作,以及OS ARB0进程的ID,ASM用它用来做所有的rebalance工作。更重要的,整个过程之中,没有任何的错误输出:

SQL> alter diskgroup testdg drop disk TESTDG_0000 NOTE: GroupBlock outside rolling migration privileged regionNOTE: requesting all-instance membership refresh for group=5Tue Jan 10 14:49:01 2017GMON updating for reconfiguration, group 5 at 222 for pid 42, osid 6197NOTE: group 5 PST updated.Tue Jan 10 14:49:01 2017NOTE: membership refresh pending for group 5/0x97f863e8 (TESTDG)GMON querying group 5 at 223 for pid 18, osid 5012SUCCESS: refreshed membership for 5/0x97f863e8 (TESTDG)NOTE: starting rebalance of group 5/0x97f863e8 (TESTDG) at power 1Starting background process ARB0SUCCESS: alter diskgroup testdg drop disk TESTDG_0000Tue Jan 10 14:49:04 2017ARB0 started with pid=39, OS id=25416 NOTE: assigning ARB0 to group 5/0x97f863e8 (TESTDG) with 1 parallel I/Ocellip.ora not found.NOTE: F1X0 copy 1 relocating from 0:2 to 2:2 for diskgroup 5 (TESTDG)NOTE: F1X0 copy 3 relocating from 2:2 to 3:2599 for diskgroup 5 (TESTDG)Tue Jan 10 14:49:13 2017NOTE: Attempting voting file refresh on diskgroup TESTDGNOTE: Refresh completed on diskgroup TESTDG. No voting file found.Tue Jan 10 14:51:05 2017NOTE: stopping process ARB0SUCCESS: rebalance completed for group 5/0x97f863e8 (TESTDG)Tue Jan 10 14:51:07 2017NOTE: GroupBlock outside rolling migration privileged regionNOTE: requesting all-instance membership refresh for group=5Tue Jan 10 14:51:10 2017GMON updating for reconfiguration, group 5 at 224 for pid 39, osid 25633NOTE: group 5 PST updated.SUCCESS: grp 5 disk TESTDG_0000 emptiedNOTE: erasing header on grp 5 disk TESTDG_0000NOTE: process _x000_+asm1 (25633) initiating offline of disk 0.3915944675 (TESTDG_0000) with mask 0x7e in group 5NOTE: initiating PST update: grp = 5, dsk = 0/0xe96892e3, mask = 0x6a, op = clearGMON updating disk modes for group 5 at 225 for pid 39, osid 25633NOTE: group TESTDG: updated PST location: disk 0001 (PST copy 0)NOTE: group TESTDG: updated PST location: disk 0002 (PST copy 1)NOTE: group TESTDG: updated PST location: disk 0003 (PST copy 2)NOTE: PST update grp = 5 completed successfully NOTE: initiating PST update: grp = 5, dsk = 0/0xe96892e3, mask = 0x7e, op = clearGMON updating disk modes for group 5 at 226 for pid 39, osid 25633NOTE: cache closing disk 0 of grp 5: TESTDG_0000NOTE: PST update grp = 5 completed successfully GMON updating for reconfiguration, group 5 at 227 for pid 39, osid 25633NOTE: cache closing disk 0 of grp 5: (not open) TESTDG_0000NOTE: group 5 PST updated.NOTE: membership refresh pending for group 5/0x97f863e8 (TESTDG)GMON querying group 5 at 228 for pid 18, osid 5012GMON querying group 5 at 229 for pid 18, osid 5012NOTE: Disk TESTDG_0000 in mode 0x0 marked for de-assignmentSUCCESS: refreshed membership for 5/0x97f863e8 (TESTDG)Tue Jan 10 14:51:16 2017NOTE: Attempting voting file refresh on diskgroup TESTDGNOTE: Refresh completed on diskgroup TESTDG. No voting file found.

因此ASM预估了9分钟的时间来完成rebalance,但实际上只使用了2分钟的时候,因此首先能知道rebalance正在做什么非常重要,然后才能知道rebalance什么时候能完成。注意,估算的时间是动态变化的,可能会增加或减少,这个依赖你的系统负载变化,以及你的rebalance的power值的设置,对于一个非常大容量的磁盘组来说,可能rebalance会花费你数小时甚至是数天的时间。

ARB0进程的跟踪文件也显示了,当前正在对哪一个ASM文件的extent的在进行重分配,也是通过这个跟踪文件,我们可以知道ARB0确实是在干着自己的本职工作,没有偷懒。

[grid@jyrac1 trace]$ tail -f +ASM1_arb0_25416.trc*** 2017-01-10 14:49:20.160ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:49:24.081ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:49:28.290ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:49:32.108ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:49:35.419ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:49:38.921ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:49:43.613ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:49:47.523ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:49:51.073ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:49:54.545ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:49:58.538ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:50:02.944ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:50:06.428ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:50:10.035ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:50:13.507ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:50:17.526ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:50:21.692ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:50:25.649ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:50:29.360ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:50:33.233ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:50:37.287ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:50:40.843ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:50:44.356ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:50:48.158ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:50:51.854ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:50:55.568ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:50:59.439ARB0 relocating file +TESTDG.256.932913341 (120 entries)*** 2017-01-10 14:51:02.877ARB0 relocating file +TESTDG.256.932913341 (50 entries)

注意,跟踪目录下的arb0的跟踪文件可能会有很多,因此我们需要知道arb0的OS是进程号,是哪一个arb0在实际做rebalance的工作,这个信息在ASM实例执行rebalance操作的时候,alert文件中会有显示。我们还可以通过操作系统命令pstack来跟踪ARB0进程,查看具体它在做什么,如下,它向我们显示了,ASM正在重分配extent(在堆栈中的关键函数 kfgbRebalExecute – kfdaExecute – kffRelocate):

[root@jyrac1 ~]# pstack 25416#0 0x0000003aa88005f4 in ?? () from /usr/lib64/libaio.so.1#1 0x0000000002bb9b11 in skgfrliopo ()#2 0x0000000002bb9909 in skgfospo ()#3 0x00000000086c595f in skgfrwat ()#4 0x00000000085a4f79 in ksfdwtio ()#5 0x000000000220b2a3 in ksfdwat_internal ()#6 0x0000000003ee7f33 in kfk_reap_ufs_async_io ()#7 0x0000000003ee7e7b in kfk_reap_ios_from_subsys ()#8 0x0000000000aea0ac in kfk_reap_ios ()#9 0x0000000003ee749e in kfk_io1 ()#10 0x0000000003ee7044 in kfkRequest ()#11 0x0000000003eed84a in kfk_transitIO ()#12 0x0000000003e40e7a in kffRelocateWait ()#13 0x0000000003e67d12 in kffRelocate ()#14 0x0000000003ddd3fb in kfdaExecute ()#15 0x0000000003ec075b in kfgbRebalExecute ()#16 0x0000000003ead530 in kfgbDriver ()#17 0x00000000021b37df in ksbabs ()#18 0x0000000003ec4768 in kfgbRun ()#19 0x00000000021b8553 in ksbrdp ()#20 0x00000000023deff7 in opirip ()#21 0x00000000016898bd in opidrv ()#22 0x0000000001c6357f in sou2o ()#23 0x00000000008523ca in opimai_real ()#24 0x0000000001c6989d in ssthrdmain ()#25 0x00000000008522c1 in main ()

Compacting

在下面的例子里,我们来看下rebalance的compacting阶段,我把上面删除的磁盘加回来,同时设置rebalance的power为2:

17:26:48 SQL> alter diskgroup testdg add disk '/dev/raw/raw7' rebalance power 2;Diskgroup altered.

ASM给出的rebalance的估算时间为6分钟:

16:07:13 SQL> select INST_ID, OPERATION, STATE, POWER, SOFAR, EST_WORK, EST_RATE, EST_MINUTES from GV$ASM_OPERATION where GROUP_NUMBER=1; INST_ID OPERA STAT POWER SOFAR EST_WORK EST_RATE EST_MINUTES---------- ----- ---- ---------- ---------- ---------- ---------- ----------- 1 REBAL RUN 10 489 53851 7920 6

大约10秒后,EST_MINUTES的值变为0.

16:07:23 SQL> / INST_ID OPERA STAT POWER SOFAR EST_WORK EST_RATE EST_MINUTES---------- ----- ---- ---------- ---------- ---------- ---------- ----------- 1 REBAL RUN 10 92407 97874 8716 0

这个时候我们在ASM的alert日志中观察到:

SQL> alter diskgroup testdg add disk '/dev/raw/raw7' rebalance power 2NOTE: GroupBlock outside rolling migration privileged regionNOTE: Assigning number (5,0) to disk (/dev/raw/raw7)NOTE: requesting all-instance membership refresh for group=5NOTE: initializing header on grp 5 disk TESTDG_0000NOTE: requesting all-instance disk validation for group=5Tue Jan 10 16:07:12 2017NOTE: skipping rediscovery for group 5/0x97f863e8 (TESTDG) on local instance.NOTE: requesting all-instance disk validation for group=5NOTE: skipping rediscovery for group 5/0x97f863e8 (TESTDG) on local instance.Tue Jan 10 16:07:12 2017GMON updating for reconfiguration, group 5 at 230 for pid 42, osid 6197NOTE: group 5 PST updated.NOTE: initiating PST update: grp = 5GMON updating group 5 at 231 for pid 42, osid 6197NOTE: PST update grp = 5 completed successfully NOTE: membership refresh pending for group 5/0x97f863e8 (TESTDG)GMON querying group 5 at 232 for pid 18, osid 5012NOTE: cache opening disk 0 of grp 5: TESTDG_0000 path:/dev/raw/raw7GMON querying group 5 at 233 for pid 18, osid 5012SUCCESS: refreshed membership for 5/0x97f863e8 (TESTDG)NOTE: starting rebalance of group 5/0x97f863e8 (TESTDG) at power 1SUCCESS: alter diskgroup testdg add disk '/dev/raw/raw7'Starting background process ARB0Tue Jan 10 16:07:14 2017ARB0 started with pid=27, OS id=982 NOTE: assigning ARB0 to group 5/0x97f863e8 (TESTDG) with 1 parallel I/Ocellip.ora not found.Tue Jan 10 16:07:23 2017NOTE: Attempting voting file refresh on diskgroup TESTDG

上面的输出意味着ASM已经完成了rebalance的第二个阶段,开始了第三个阶段compacting,如果我说的没错,通过pstack工具可以看到kfdCompact()函数,下面的输出显示,确实如此:

# pstack 982#0 0x0000003957ccb6ef in poll () from /lib64/libc.so.6...#9 0x0000000003d711e0 in kfk_reap_oss_async_io ()#10 0x0000000003d70c17 in kfk_reap_ios_from_subsys ()#11 0x0000000000aea50e in kfk_reap_ios ()#12 0x0000000003d702ae in kfk_io1 ()#13 0x0000000003d6fe54 in kfkRequest ()#14 0x0000000003d76540 in kfk_transitIO ()#15 0x0000000003cd482b in kffRelocateWait ()#16 0x0000000003cfa190 in kffRelocate ()#17 0x0000000003c7ba16 in kfdaExecute ()#18 0x0000000003c4b737 in kfdCompact ()#19 0x0000000003c4c6d0 in kfdExecute ()#20 0x0000000003d4bf0e in kfgbRebalExecute ()#21 0x0000000003d39627 in kfgbDriver ()#22 0x00000000020e8d23 in ksbabs ()#23 0x0000000003d4faae in kfgbRun ()#24 0x00000000020ed95d in ksbrdp ()#25 0x0000000002322343 in opirip ()#26 0x0000000001618571 in opidrv ()#27 0x0000000001c13be7 in sou2o ()#28 0x000000000083ceba in opimai_real ()#29 0x0000000001c19b58 in ssthrdmain ()#30 0x000000000083cda1 in main ()

通过tail命令查看ARB0的跟踪文件,发现relocating正在进行,而且一次只对一个条目进行relocating。(这是正进行到compacting阶段的另一个重要线索):

$ tail -f +ASM1_arb0_25416.trcARB0 relocating file +DATA1.321.788357323 (1 entries)ARB0 relocating file +DATA1.321.788357323 (1 entries)ARB0 relocating file +DATA1.321.788357323 (1 entries)...

compacting过程中,V$ASM_OPERATION视图的EST_MINUTES字段会显示为0(也是一个重要线索):

16:08:56 SQL> / INST_ID OPERA STAT POWER SOFAR EST_WORK EST_RATE EST_MINUTES---------- ----- ---- ---------- ---------- ---------- ---------- ----------- 2 REBAL RUN 10 98271 98305 7919 0

固态表X$KFGMG的REBALST_KFGMG字段会显示为2,代表正在compacting。

16:09:12 SQL> select NUMBER_KFGMG, OP_KFGMG, ACTUAL_KFGMG, REBALST_KFGMG from X$KFGMG;NUMBER_KFGMG OP_KFGMG ACTUAL_KFGMG REBALST_KFGMG------------ ---------- ------------ ------------- 1 1 10 2

一旦compacting阶段完成,ASM的alert 日志中会显示stopping process ARB0 和rebalance completed:

Tue Jan 10 16:10:19 2017NOTE: stopping process ARB0SUCCESS: rebalance completed for group 5/0x97f863e8 (TESTDG)

一旦extents relocation完成,所有的数据就已经满足了冗余度的要求,不再会担心已经失败磁盘的partern磁盘再次失败而出现严重故障。

Changing the power

Rebalance的power可以在磁盘组rebalance过程中动态的更改,如果你认为磁盘组的默认级别太低了,可以去很容易的增加它。但是增加到多少呢?这个需要你根据你系统的IO负载,IO吞吐量来定。一般情况下,你可以先尝试增加到一个保守的值,例如5,过上十分钟看是否有所提升,以及是否影响到了其他业务对IO的使用,如果你的IO性能非常强,那么可以继续增加power的值,但是就我的经验来看,很少能看到power 的设置超过30后还能有较大提升的。测试的关键点在于,你需要在你生产系统的正常负载下去测试,不同的业务压力,不同的存储系统,都可能会让rebalance时间产生较大的差异。

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