Understanding Exadata

-

 Exadata:

Oracle Exadata is a part of Oracle Engineered Family 

Oracle Exadata Database Machine is engineered to be the highest performing and most available platform for running Oracle Database.

It is a combination of Oracle Compute nodes and Oracle Storage nodes 

A typical Exadata machine contains 

-> Compute nodes (3,4,8)

-> Storage nodes called as cell servers (14 cells with each cell containing 12 physical disks )

-> 2 infi band switches(for intra node communication)

-> 1 cisco switch 

-> 1 spine switch to group one or more  exadata machines

-> each cell contains 4 flash cells with 6.5 TB (6.5 * 4 = 27 TB approx)


Storage server runs on OLE6/7 installed with cell software to manage the cells 



Some Important Points :

============== 

ASM disk group will be created on grid disk -> cell -> LUN -> physical disks

asm_diskstring  /o/cell ip/grid disk


How to manage Exadata:

===============

cellcli -> used to login on a storage server and can manage single cell server 

dcli -> distributed cli used to manage all the cell servers 

DBMCLI -> works on each compute node to manage cell servers

EXAcli -> used to connect to the cell server on remote host 

IDB -> intelligent protocol used by the compute nodes and database nodes to transfer the data, it works on reliable data gram sockets 

ILOM -> called as Integrated lights out managers is a special piece of hardware with embodied software.

ILOM proactively manage the following

Identify hardware error and faults
Remotely control the power of the node
View current status of sensors and indicators of the system
Identify the hardware configuration of the system
Receive alerts that are generated about system events
ILOM proactively manage the following:

Identify hardware error and faults
Remotely control the power of the node
View the graphical and non-graphical console of the host
View current status of sensors and indicators of the system
Identify the hardware configuration of the system
Receive alerts that are generated about system events


Exadata Features:

  • Smart flash cache 
  • Smart flash log
  • Smart Scan
  • HCC
  • IORM
How to enable smart scan :
cell_smart_scan_capable=true
cell_offloading_processing=true
Smart scan works for 
full table /full index/direct_path 
to enable direct path _serial_direct-read=true
Smart scan is not useful during 

  • concurrent DML 
  • Excessive Row chaining 
  • if data already in buffer cache then it won't process
  • Storage server CPU utilization more that database server 
Storage index helps in eliminating I/O processing by identifying storage regions without values 
To enable flash cache we can mention 
cell_flash_cache -> default/keep/none
None -Exclude the object from the flash cache entirely.
default -> Give the object a normal priority for caching
Keep -> Give the object a higher priority for caching


Flash cache  write through -> DML directly to disk 
Flash cache write back -> DML to flash cache then to disk 







  


Comments

Post a Comment

Popular posts from this blog

Understanding Terraform

-
 Terraform is a tool used  for building, changing, and versioning infrastructure safely and efficiently. A Terraform can manage multiple cloud services using a provider plugin  Terraform work flow? Terraform work flow will be comprised of validate -> plan -> apply and finally destroy. what is the important file of terraform which records the actions of Terraform apply? For every Terraform execution the action will be recorded in a file called Terraform state file .  The terraform init command is used to initialise a working directory containing Terraform configuration files. During init, the configuration is searched for module blocks, and the source code for referenced modules is retrieved from the locations given in  their source arguments. The terraform plan command is used to create an execution plan. It will not modify things in infrastructure. The terraform apply command is used to apply the changes required to reach the desired state of the configur...
Read more

How to make CRS and ASM not to restart after server reboot

-
I have noticed that server rebooting is taking lot of time on a VM machine for every reboot, so I have decided to auto start of the crs and ASM service During this phase I have noticed an attribute called auto_start when I try to execute the below command crsctl stat res -p This AUTO_START attribute is there for several resources like ora.ASM ,ora.crs,ora.DATA_DG it has got 2 options restore(0) , never(2) and always (1) always (1)  Causes the resource to restart when the node restarts regardless of the resource’s state when the node stopped -restore (0)  Does not start the resource at restart time if it was in an offline state, such as STATE=OFFLINE, TARGET=OFFLINE, when the node stopped. The resource is restored to its state when the node went down. The resource is started only if it was online before and not otherwise. -never (2)  Oracle Clusterware never restarts the resource regardless of the resource’s state when the node is stopped. So I have dec...
Read more

How to repair ASM disk header

-
Image
What is ASM disk header corruption? ASM disk header corruption is a loss or damage to the disk header which contains the metadata essential for the operation and availability of an ASM disk group in Oracle. Imagine that you have an ASM disk corruption in any of the ASM diskgroups that have critical business data and the diskgroup has been configured as "EXTERNAL" redundancy, meaning that if one disk is inaccessible the whole diskgroup will be unavailable. Now what? Is your only option to restore it from backup by recreating the diskgroup or are there any other faster ways to recover the data? Here you need to find out whether it’s a complete loss of data in the ASM disk or is it just a header corruption. Hopefully for you, this is just a header corruption. Because, yes, there is a way out!  Below find the steps to restore from the ASM header corruption. Most of the data in the ASM disk header is of interest to that disk only. However, some information in the ASM disk header ...
Read more