About ASM redundancy

Xiaobai asks

1、 If in ASMCA This step creates a data disk group DATADG;

2、 Then select /dev/asmdisk1 and /dev/asmdisk2（ The above is the network diagram , Suppose there are three devices , It's big and small 10GB）;

3、 Redundancy mechanism selection “Normal”, Click on OK The creation is complete .

Please tell me about the disk group created in this way , Last in v$asm_diskgroup What I saw in it total_mb Size is 30GB, But in fact, is there only 10GB Well ？

Because of the others 2 The first device is a mirror ？ I don't know if it's understood like this .

Operation and maintenance Xiaobai deployed according to the document for the first time RAC, Copy sth. without catching its spirit , I have no idea , Please give me some advice .

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Take the answer 1：

You know ORACLE ASM You will know the three redundancy methods provided

Generally, the three modes require disk groups ：
external  1 block
normal    3 block
high        5 block

1、 External redundancy （external redundancy）：
Express Oracle I don't want to help you manage the image , The function is implemented by an external storage system , Such as through RAID technology ; Effective disk space is the sum of all disk device spaces .

2、 Default redundancy （normal redundancy）：
Express Oracle Provide 2 Copy the image to protect the data ( Mirror data once ), Effective disk space is the sum of the sizes of all disk devices 1/2 （ Most used ）.

3、 Highly redundant （high redundancy）：
Express Oracle Provide 3 Copy the image to protect the data ( Mirror the data twice ), To improve performance and data security , You need at least three disks （ Three failure group）;
Effective disk space is the sum of the sizes of all disk devices 1/3, Although the redundancy level is high , But hardware costs the most .

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Other answers 1：

You know ORACLE ASM You will know the three redundancy methods provided

Generally, the three modes require disk groups ：
external  1 block
normal    3 block
high        5 block

1、 External redundancy （external redundancy）：
Express Oracle I don't want to help you manage the image , The function is implemented by an external storage system , Such as through RAID technology ; Effective disk space is the sum of all disk device spaces .

2、 Default redundancy （normal redundancy）：
Express Oracle Provide 2 Copy the image to protect the data ( Mirror data once ), Effective disk space is the sum of the sizes of all disk devices 1/2 （ Most used ）.

3、 Highly redundant （high redundancy）：
Express Oracle Provide 3 Copy the image to protect the data ( Mirror the data twice ), To improve performance and data security , You need at least three disks （ Three failure group）;
Effective disk space is the sum of the sizes of all disk devices 1/3, Although the redundancy level is high , But hardware costs the most .

Other answers 2：

combination ORACLE ASM The three redundancy methods provided and the following interface should help you better understand . The following figure is the network diagram , Prepare for your reality .

Find a testing machine , Try all three redundancy methods .
I hope it helped you
If you are satisfied with the answer , Please click the adopt button ！

Other answers 3：

Thank you for your answers ！ Then what I understand should be right , If I create a disk group , Choose 3 block 10GB The size of the disk , Redundancy mechanism selection Normal, stay V$ASM_DISKGROUP What you see total_mb The total size seen is 30GB, But what is actually available is 10GB nothing more , Is that right

Other answers 4：

That's over , I have a 500G The data of should be put into storage , Do you need to delete the disk group and rebuild

Other answers 5：

No need to delete the reconstruction , You can add new disk groups

https://www.modb.pro/doc/182

Other answers 6：

And new disk groups , Disk redundancy is also Normal

Other answers 7：

Then rebuild it