12c以后ASM单盘大小可超2TB

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发布时间：2019-04-28

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

Version 19.9.0.0.0

oracle19.9默认asm的compatbile.rdbms为11.2.0.4，所以每个磁盘还是应小于2TB

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

SOLUTION

12cR1

The following information was taken from the .

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

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.

Recommendations for Storage Preparation

Recommendations for storage preparation with Oracle ASM are discussed in this topic.

The following are guidelines for preparing storage for use with Oracle ASM:

Configure a separate disk group for the following:
- Oracle Cluster Registry (OCR) and voting files
- Grid Infrastructure Management Repository (GIMR) files
- Database data files
- Fast recovery area

The number of LUNs (Oracle ASM disks) for each disk group should be at least equal to four times the number of active I/O paths. For example, if a disk group has two active I/O paths, then minimum of eight LUNs should be used. The LUNs should be of equal size and performance for each disk group.

An I/O path is a distinct channel or connection between storage presenting LUNs and the server. An active I/O path is an I/O path in which the I/O load on a LUN is multiplexed through multipathing software.

Ensure that all Oracle ASM disks in a disk group have similar storage performance and availability characteristics. In storage configurations with mixed speed drives, such as flash memory and hard disk drives (HDD), I/O performance is constrained by the slowest speed drive.

Oracle ASM data distribution policy is capacity-based. Ensure that Oracle ASM disks in a disk group have the same capacity to maintain balance.

Configure a minimum of three failure groups for normal redundancy disk groups and five failure groups for high redundancy disk groups to maintain the necessary number of copies of the Partner Status Table (PST) to ensure robustness with respect to storage hardware failures.

Create external redundancy disk groups when using high-end storage arrays. High-end storage arrays generally provide hardware RAID protection. Use Oracle ASM mirroring redundancy when not using hardware RAID, or when you need host-based volume management functionality, such as mirroring across storage systems. You can use Oracle ASM mirroring in configurations when mirroring between geographically-separated sites (extended clusters).