关于asm磁盘的大小限制2T问题？

需注意oracle19c默认创建asm磁盘组的时候compatbile.rdbms可能为11.2.0.4或10.1，并没有大于等于12.1，所以规划时每个磁盘还是应小于2TB，如果要大于2T,请修改compatbile.rdbms为大于等于12.1


例如，如果数据库的COMPATIBLE初始化参数设置为12.2，那么COMPATIBLE.RDBMS可以设置为10.1和12.2之间的任何值。
如果数据库的兼容初始化参数设置为19.0，则COMPATIBLE.RDBMS可以设置为10.1和19.0之间的任何值。

参考：https://docs.oracle.com/en/database/oracle/oracle-database/19/ostmg/diskgroup-compatibility.html#GUID-338AF92B-CA16-4FAD-A635-FEBC803D9EF2

在你的环境也可查查：

asmcmd lasttr -l -G DATA

关于2t问题参考如下两篇文章：

Can I Create an 11.2 Disk Over the 2 TB Limit? (Doc ID 1077784.1)

SOLUTION
In 11.2 a check was made to disallow creation of diskgroups with disks of size > 2tb.

If a disk > 2tb is used to create a diskgroup, ORA-15099 error will come up. 

Disk size greater than 2 TB can only be used on 12.1 release when  compatible.asm  and compatible.rdbms is set to  12.1  or higher.

What Is The Max LUN Size In ASM 12c ? (Doc ID 1667736.1)

GOAL
What is the Max LUN size in ASM 12c (not using Flex ASM).

Before ASM 12c there was an limitation of 2 Tb LUNs.
 

SOLUTION
12cR1
The following information was taken from the Oracle® Automatic Storage Management Administrator's Guide
12c Release 1 (12.1) under Oracle ASM Storage Limits.

To use these limits must use compatible.asm and compatbile.rdbms set to 12.1.

Before 12c, the limit was 2TB per disk. Here is what the documentation states:

Without any Oracle Exadata Storage, Oracle ASM has the following storage limits if the COMPATIBLE.ASM disk group attribute is set to 12.1 or greater:

4 PB maximum storage for each Oracle ASM disk with the allocation unit (AU) size equal to 1 MB

8 PB maximum storage for each Oracle ASM disk with the AU size equal to 2 MB

16 PB maximum storage for each Oracle ASM disk with the AU size equal to 4 MB

32 PB maximum storage for each Oracle ASM disk with the AU size equal to 8 MB

320 exabytes (EB) maximum for the storage system

 

12cR2
The following information was extracted from the following documentation: 

Administrator's Guide

Performance and Scalability Considerations for Disk Groups

https://docs.oracle.com/en/database/oracle/oracle-database/12.2/ostmg/performance-scability-diskgroup.html#GUID-F0FCF3FE-C2A2-4B06-99A3-8432790C0EC4

 

Oracle ASM Storage Limits

Oracle ASM provides near unlimited capacity for future growth, but does have some storage limits.

Oracle ASM has the following limits on the number of disk groups, disks, and files:

511 disk groups in a storage system for Oracle Database 12c Release 1 or later

10,000 Oracle ASM disks in a storage system

1 million files for each disk group

Without any Oracle Exadata Storage, Oracle ASM has the following storage limits if the COMPATIBLE.ASM or COMPATIBLE.RDBMS disk group attribute is set to less than 12.1:

2 terabytes (TB) maximum storage for each Oracle ASM disk

20 petabytes (PB) maximum for the storage system

Without any Oracle Exadata Storage, Oracle ASM has the following storage limits if the COMPATIBLE.ASM and COMPATIBLE.RDBMS disk group attributes are set to 12.1 or greater:

4 PB maximum storage for each Oracle ASM disk with the allocation unit (AU) size equal to 1 MB

8 PB maximum storage for each Oracle ASM disk with the AU size equal to 2 MB

16 PB maximum storage for each Oracle ASM disk with the AU size equal to 4 MB

32 PB maximum storage for each Oracle ASM disk with the AU size equal to 8 MB

320 exabytes (EB) maximum for the storage system

With all Oracle Exadata Storage, Oracle ASM has the following storage limits:

4 PB maximum storage for each Oracle ASM disk with the AU size equal to 1 MB

8 PB maximum storage for each Oracle ASM disk with the AU size equal to 2 MB

16 PB maximum storage for each Oracle ASM disk with the AU size equal to 4 MB

32 PB maximum storage for each Oracle ASM disk with the AU size equal to 8 MB

320 EB maximum for the storage system

The maximum size limit of a disk group equals the maximum disk size multiplied by the maximum number of disks in a disk group (10,000).

The maximum number of disks across all disk groups is 10,000. The 10,000 disks can be in one disk group or distributed across a maximum of 511 disk groups. This is a limitation on the number of Oracle ASM disks, not necessarily the number of spindles. A storage array could group multiple spindles into a LUN that is used as a single Oracle ASM disk.

File size limits are dependent on the value of the disk group compatibility attributes. Oracle ASM supports file sizes greater than 128 TB in any redundancy mode when the COMPATIBLE.RDBMS disk group attribute is set greater than 10.1.

If COMPATIBLE.RDBMS is set to 10.1, the file size limits are less. For example, with COMPATIBLE.RDBMS equal to 10.1 and the AU size equal to 1 MB, Oracle ASM file size limits are:

External redundancy: 16 TB

Normal redundancy: 5.8 TB

High redundancy: 3.9 TB

Note:

Oracle Database supports data file sizes up to 128 TB depending on the file system. In addition, Oracle Database has a file size limit that is dependent on the DB_BLOCK_SIZE initialization parameter.