OOW Notes - ASM New Features on 12c

Thursday 12:30 - ASM New features

• simple idea
  
• 1to1 ASM to server
  
• shared disk groups
  
• wide file striping
  
• 10years old in oracle database
  

grid computing .. cloud computing

• more consolidation → more database instances per node
  
• more clustering → more nodes in clusters
  
• larger storage configurations
  

ASM evolves

• maximize ASM robustness because increased number of database instances running on large servers
  
• minimize ASM overhead because of large clusters
  
• minimize cluster reconfiguration overhead because of large clusters
  

engineered systems (EXADATA and database appliance)

• complete solutions
  
• optimized for a particular objective
  
• storage management provided by ASM
  
• storage cells provides management offloading
  

flex ASM (NEW)

• eliminate requirement for an ASM instance on every cluster server
  
• database instances connect any ASM instance in the clustering database instances can failover to a secondary ASM instance
  
• admins specify the cardinality of the ASM instances (default 3)
  

ASM network
in the previous version an oracle cluster required:

• public network for client applications
  
• one or more private networks for interconnect communication within the cluster
  

remote access (NEW)
in the previous versions database instances use os authentication to connect ASM
ASM clients and the server are always on the same server so this should change


12c database instance and ASM servers can be on different servers

• flex ASM users password file authentication
  
• password file in the ASM diskgroup
  
• default config. is configured with the ASM installation
  

other flex features

• increased mac number of disks to 511 (previous 63)
  
• command for renaming ASM disk
  
• ASM instance patch-level verification
  
• replicated physical metadata
  
• improves reliability
  
• virtual metadata has always been replicated with ASM mirroring
  

admins can now specify a failure group repair time (NEW)

• similar to existing disk repair time
  
• new diskgroup attributes; failgroup_repair_time
  
• default time 24 hours
  
• power limit can be set for disk resync. operations
  
• Conceptually similar to power limit setting for disk group rebalance
  
• rebalance: 1 (least resource) to 1024 most resources
  

disk rescync now check points (NEW)
interrupted resync operations are automatic restart


sometimes rebalance operations are required to restore redundancy.
Example:
a disk fails and no replacement available
HBA containing a failure group goes offline

• with oracle database flex ASM optimized reorganization
  
• critical files such as control files log files are restored before datafiles
  
• secondary failure is less likely result in critical file loss
  
• 
  
• admins can now specify the content type for each disk group:
  
• new disk group attribute; content.type (possible values data, recovery or system)
  

• disk group primary/secondary partnering changes with content.type
  
• decreases likelihood that multiple failures cause data loss
  

silent data corruption is a fact in todays storage world

• database checks for logical consistency when reading data
  
• if a logical corruption is detected then automatic recovery can be performed using ASM mirror copies
  
• for seldom accessed data, over time all mirror copies of the data could be corrupted
  
  
• with oracle db 12c data can be proactively scrubbed (NEW)
  

• scrubbing occurs automatically during rebalance operations
  

• with flex ASM, most rebalance tasks offloaded to EXADATA storage
  
• each offload request can replace numerous IO
  

IO distribution in 12c (NEW)

• each read request is sent to at least loaded available disk
  
• even read is transparent to apps and enabled default
  
• users on IO bound systems should notice a performance improvement
  

managing flex ASM (nothing changes)

• srvctl status asm
  
• srvctl modifiy asm -count 4
  
• srvctl start asm -n node_name
  
• srvctl stop asm -n nodename
  

ASM Trivia's


why power limit setting value to 11. Why 11?


what was it is called before ASM?


all asm file extent pointers are protected from corruption by XORing to a constant.. what is that constant? 42



The acronym describing ASM data allocation and protection policy is LIKE what?

Add/Remove ASM disks and asm_power_limit

Before going live on production our storage team decided to reconfigure their storage and raidsets for better performance. So i gave the raw devices back from asm and of course used the opportunity to test the asm_power_limit parameter.

From the following listing you can find how to list asm disks, adding and removing disks from a disk group and watch the rebalance operation from v$asm_operation view.

By changing the init parameter "asm_power_limit", asm rebalance operations are significantly getting faster. The difference can obviously be seen by setting the parameter to 10 (instead of default value 1) and then giving the same operations that need rebalance. Of course this was not an online system so we may want asm to exhaust all the IO for rebalancing. But in case of production systems there can be unwanted IO performance degradation of the application by this kind of aggressive setting.

SQL> select group_number,state,name,total_mb from v$asm_disk;

GROUP_NUMBER STATE    NAME                   TOTAL_MB
------------ -------- -------------------- ----------
0 NORMAL                               924
0 NORMAL                               924
0 NORMAL                               924
0 NORMAL                               924
1 NORMAL   DATA_0009                614300
1 NORMAL   DATA_0008                614290
1 NORMAL   DATA_0002                614290
1 NORMAL   DATA_0001                614290
1 NORMAL   DATA_0000                614290
1 NORMAL   DATA_0007                614290
1 NORMAL   DATA_0006                614290
1 NORMAL   DATA_0005                614290
1 NORMAL   DATA_0004                614290
1 NORMAL   DATA_0003                614290

14 rows selected.

SQL> alter diskgroup DATA drop disk DATA_0000;

Diskgroup altered.

SQL> alter diskgroup DATA drop disk DATA_0001;

Diskgroup altered.

SQL> select group_number,state,name,total_mb,label,path from v$asm_disk;

GROUP_NUMBER STATE    NAME              TOTAL_MB LABEL PATH
------------ -------- --------------- ---------- ----- --------------------------------------------------
0 NORMAL                          924       /dev/rdsk/c6t600601607D731F00A8833C0377FEDD11d0s0
0 NORMAL                          924       /dev/rdsk/c6t600601607D731F00A7833C0377FEDD11d0s0
0 NORMAL                          924       /dev/rdsk/c6t600601607D731F00A6833C0377FEDD11d0s0
0 NORMAL                          924       /dev/rdsk/c6t600601607D731F006596A6CD2CE9DD11d0s0
1 NORMAL   DATA_0009           614300       /dev/rdsk/c6t600601607D731F00D994060263E8DD11d0s0
1 NORMAL   DATA_0008           614290       /dev/rdsk/c6t600601607D731F00D894060263E8DD11d0s0
1 NORMAL   DATA_0002           614290       /dev/rdsk/c6t600601607D731F006A37A4E0A0E7DD11d0s0
1 DROPPING DATA_0001           614290       /dev/rdsk/c6t600601607D731F006937A4E0A0E7DD11d0s0
1 DROPPING DATA_0000           614290       /dev/rdsk/c6t600601607D731F006837A4E0A0E7DD11d0s0
1 NORMAL   DATA_0007           614290       /dev/rdsk/c6t600601607D731F007608DB3DA0E7DD11d0s0
1 NORMAL   DATA_0006           614290       /dev/rdsk/c6t600601607D731F007508DB3DA0E7DD11d0s0
1 NORMAL   DATA_0005           614290       /dev/rdsk/c6t600601607D731F007408DB3DA0E7DD11d0s0
1 NORMAL   DATA_0004           614290       /dev/rdsk/c6t600601607D731F007308DB3DA0E7DD11d0s0
1 NORMAL   DATA_0003           614290       /dev/rdsk/c6t600601607D731F007208DB3DA0E7DD11d0s0


SQL> select * from v$asm_operation;

OPERA STAT      POWER     ACTUAL      SOFAR   EST_WORK   EST_RATE EST_MINUTES
----- ---- ---------- ---------- ---------- ---------- ---------- -----------
REBAL RUN          10         10       7198      12996        260          22
REBAL RUN          10         10       7679      12979        242          21
REBAL RUN          10         10       9286      12930        201          18
REBAL RUN          10         10      11647      12899        237           5

SQL> select * from v$asm_operation;

no rows selected

SQL> select group_number,state,name,total_mb,label,path from v$asm_disk;

GROUP_NUMBER STATE    NAME              TOTAL_MB LABEL PATH
------------ -------- --------------- ---------- ----- --------------------------------------------------
0 NORMAL                          924       /dev/rdsk/c6t600601607D731F00A8833C0377FEDD11d0s0
0 NORMAL                          924       /dev/rdsk/c6t600601607D731F00A7833C0377FEDD11d0s0
0 NORMAL                          924       /dev/rdsk/c6t600601607D731F00A6833C0377FEDD11d0s0
0 NORMAL                       614290       /dev/rdsk/c6t600601607D731F006937A4E0A0E7DD11d0s0
0 NORMAL                       614290       /dev/rdsk/c6t600601607D731F006837A4E0A0E7DD11d0s0
0 NORMAL                          924       /dev/rdsk/c6t600601607D731F006596A6CD2CE9DD11d0s0
1 NORMAL   DATA_0009           614300       /dev/rdsk/c6t600601607D731F00D994060263E8DD11d0s0
1 NORMAL   DATA_0008           614290       /dev/rdsk/c6t600601607D731F00D894060263E8DD11d0s0
1 NORMAL   DATA_0002           614290       /dev/rdsk/c6t600601607D731F006A37A4E0A0E7DD11d0s0
1 NORMAL   DATA_0007           614290       /dev/rdsk/c6t600601607D731F007608DB3DA0E7DD11d0s0
1 NORMAL   DATA_0006           614290       /dev/rdsk/c6t600601607D731F007508DB3DA0E7DD11d0s0
1 NORMAL   DATA_0005           614290       /dev/rdsk/c6t600601607D731F007408DB3DA0E7DD11d0s0
1 NORMAL   DATA_0004           614290       /dev/rdsk/c6t600601607D731F007308DB3DA0E7DD11d0s0
1 NORMAL   DATA_0003           614290       /dev/rdsk/c6t600601607D731F007208DB3DA0E7DD11d0s0


SQL> alter diskgroup DATA add disk '/dev/rdsk/c6t600601607D731F006837A4E0A0E7DD11d0s0';

Diskgroup altered.

SQL> select group_number,state,name,total_mb,label,path from v$asm_disk;

GROUP_NUMBER STATE    NAME              TOTAL_MB LABEL PATH
------------ -------- --------------- ---------- ----- --------------------------------------------------
0 NORMAL                          924       /dev/rdsk/c6t600601607D731F00A8833C0377FEDD11d0s0
0 NORMAL                          924       /dev/rdsk/c6t600601607D731F00A7833C0377FEDD11d0s0
0 NORMAL                          924       /dev/rdsk/c6t600601607D731F00A6833C0377FEDD11d0s0
0 NORMAL                       614290       /dev/rdsk/c6t600601607D731F006937A4E0A0E7DD11d0s0
0 NORMAL                          924       /dev/rdsk/c6t600601607D731F006596A6CD2CE9DD11d0s0
1 NORMAL   DATA_0009           614300       /dev/rdsk/c6t600601607D731F00D994060263E8DD11d0s0
1 NORMAL   DATA_0008           614290       /dev/rdsk/c6t600601607D731F00D894060263E8DD11d0s0
1 NORMAL   DATA_0002           614290       /dev/rdsk/c6t600601607D731F006A37A4E0A0E7DD11d0s0
1 NORMAL   DATA_0007           614290       /dev/rdsk/c6t600601607D731F007608DB3DA0E7DD11d0s0
1 NORMAL   DATA_0006           614290       /dev/rdsk/c6t600601607D731F007508DB3DA0E7DD11d0s0
1 NORMAL   DATA_0005           614290       /dev/rdsk/c6t600601607D731F007408DB3DA0E7DD11d0s0
1 NORMAL   DATA_0004           614290       /dev/rdsk/c6t600601607D731F007308DB3DA0E7DD11d0s0
1 NORMAL   DATA_0003           614290       /dev/rdsk/c6t600601607D731F007208DB3DA0E7DD11d0s0
1 NORMAL   DATA_0000           614290       /dev/rdsk/c6t600601607D731F006837A4E0A0E7DD11d0s0


SQL> show parameter asm_power_limit;

NAME                            TYPE        VALUE
------------------------------- ----------- -------------------------
asm_power_limit                 integer     1

SQL> alter system set asm_power_limit=10;

System altered.

SQL> show parameter asm_power_limit;

NAME                            TYPE        VALUE
------------------------------- ----------- -------------------------
asm_power_limit                 integer     10

SQL>