RAID 0 + 1 Study Notes

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• Abstract: RAID 0 + 1 is a combination of data block segments and disk images. When RAID 0 + 1 appears, the segmentation technology of the Oracle layer is eliminated, because the segments of RAID 0 + 1 are at the data block layer, and the table block allocation method is as follows: each data block on a disk spans every disk device.
• Labels: RAID 0 + 1

RAID 1 is also called a disk image. After a long history of RAID development, many users are familiar with RAID 0 + 1. Here I will share my personal understanding and discuss it with you. RAID, a Redundant Array of cheap disks, is a method of storing the same data in different locations on multiple hard disks. RAID has many different types (called RAID "level"). Each type has its own advantages and disadvantages.

For Oracle9i databases, many RAID solutions do not have the high performance required by Oracle databases. Most Oracle experts choose a RAID solution that combines mirroring and block-level striping.

It is important to note that RAID does not prevent catastrophic disk faults. We recommend that you run all the databases in ARCHIVELOG mode without considering the RAID architecture. Oracle also recommends regular Oracle backup.

Remember, the I/O subsystem consists of many components, including controllers, channels, and disk adapters, and the SCSI adapter-any crash of these components will cause irreparable disk errors to your database. Now let's take a look at the most common RAID architecture of Oracle databases.

RAID 0 usually refers to the segmentation technology of data blocks. It is an excellent method to achieve load balancing of Oracle databases on disk devices, but because it does not provide data backup, therefore, high availability is completely unavailable. Unlike manual data file segmentation (you need to manually split Oracle table space into small data files, oracle uses RAID 0 to automatically segment A data block and store it in all disk devices at a time. In this way, each data file contains a part of its content on each disk, so that the disk I/O load will become very balanced.

RAID 1 is also called a disk image. Because disks are replicated to each other, RAID 1 can be a dual or triple image. According to the RAID 1 architecture design, if a disk error occurs, the I/O Sub-system will automatically switch to one of each replication disk without service interruption. Oracle Experts use RAID 1 when demanding high availability. For a triple image, the mean time to failure (MTTF) of the Oracle database can be up to decades.

RAID 0 + 1 is a combination of data block segments and disk images. When RAID 0 + 1 appears, the segmentation technology of the Oracle layer is eliminated, because the segments of RAID 0 + 1 are at the data block layer, and the table block allocation method is as follows: each data block on a disk spans every disk device.

RAID 0 + 1 is also a much better alternative to (simple) segmentation technology because it distributes load evenly to all disk devices, that is to say, the increase and decrease of the load are evenly distributed to all disks. This reduces the burden on Oracle system administrators to manually segment Oracle tables on each disk.

RAID 5 some newer hardware-based RAID 5 storage solutions are extremely suitable as data warehouses. RAID 5 is a good way to build an Oracle data warehouse, because the load speed is not very important here, and the primary responsibility of system I/O is read-only activities.

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