Oracle raid usage

We usually have no choice at the raid array level when deploying servers. RAID technology has grown into dozens of categories today, but there are only a few commonly used in production systems, for example, 0, 1, 5, 0 + 1. Readers may be familiar with the raid principles of various levels and may even be able to recite them. However, when selecting the most suitable raid level for the application system in the production system, there may not be much psychological potential. This article will introduce Oracle database servers when selecting the raid array level, hoping that people who have doubts will take a reassurance.

First, let's take a look at the advantages and disadvantages of several commonly used RAID levels.

Raid level	Advantages and disadvantages
Raid not required	Any raid has certain management overhead. If you need data writing speed and do not need to protect data, you can choose not to use raid, if you have three hard disks, you can use one of them to install the operating system and database software, the second to store data files, and the third to store log files, in this way, the overall performance of the system will be very good, but if any hard disk is damaged, the system maintenance time will be relatively long. Of course, if you still have more hard disks, the work of each hard disk can be further refined, for example, a dedicated storage control file and parameter file, and multiple Data files are separated. Each file is a hard disk, which can only be said to be of great performance.
Raid0	Anyone familiar with RAID 0 knows that it has the highest read/write speed, because after data is divided into small blocks, data is synchronously written to multiple hard disks across multiple hard disks, in this way, the write speed is very fast. If you do not believe it, you can make up three hard disks into RAID 0, and then install the operating system, you will find that the installation time is much reduced. Of course, the speed of reading data is significantly higher than that of a single hard disk, but there are not many such raid users, because once one hard disk breaks down, professional recovery companies may need to recover data. RAID 0 is very suitable for caching those servers as proxies. It requires speed.
Raid1	Raid 1 is designed to ensure data security. It is usually called an image. If you make two hard disks into RAID 1, in this case, the size of the hard disk you see in the operating system is only one disk and the other disk is used as an image. In this case, one copy of data is saved in two copies, it is allowed to break one of them without affecting the normal use of the operating system and applications, but its disadvantage is that the write speed is lower than that of a single hard disk. After all, write twice during write operations, it will certainly consume a certain amount of CPU time slice. This raid is suitable for applications that focus on data security, such as financial software.
Raid0 + 1	It can be seen from its name that this is a combination of RAID 0 and RAID 1 technology. It also utilizes the high speed feature of RAID 0 and the image feature of RAID 1, this satisfies the needs of users who pay the same attention to speed and data security. To implement this raid, at least four hard disks are required, so that one of them can be damaged without affecting the operating system and applications. It is applicable to fields that require both access to a large amount of data and strict data security requirements, such as banking and finance.
RAID 5	RAID 5 can be understood as a compromise between RAID 0 and RAID 1. RAID 5 has a Data Reading Speed similar to RAID 0, but only requires an additional parity information, data Writing speed is slower than writing data to a single disk. At the same time, because multiple data correspond to one parity information, the disk space utilization of RAID 5 is higher than that of RAID 1, and the storage cost is relatively low. To implement this raid, at least three hard disks are required, so that one of them can be damaged without affecting the operating system and applications.

Which raid is the proper choice for the server to install Oracle? What I want to tell you is that there is no final conclusion. To make the final performance of your Oracle Server better, the following is a feasible method I have summarized.

First, plan which disks are used to store the files, then check the read/write performance requirements of these files, and then create a raid-level Array Based on the performance requirements. The following are the file type and raid level recommended for Oracle, and the reasons for the recommendation are described:

<! --. Style1 {color: # ffffff; font-weight: bold;} -->

File Type	Recommended raid level	Reason for recommendation
Control File	Raid not required RAID 0 RAID 0 + 1	I recommend three RAID levels to store control files. Because control files are updated frequently, the faster the speed, the better. However, you must be careful when using RAID 0 or when using RAID storage control files. to back up the files properly, you must also note that multiple control files are recommended, maybe the others are better, so that we can directly use the control file to overwrite the broken ones for recovery.
Online redo Log Files	Raid not required RAID 0 RAID 0 + 1	Similar to control files, online redo log files are frequently updated. You must consider using a fast raid level. We recommend that you use multiple online redo log files.
Temporary data File	Raid not required RAID 0	Temporary files focus on fast access and do not care about their reliability. If data files are lost, they can be quickly rebuilt in the same place. Therefore, we recommend that you use RAID 0 or not.
Archive logs File	Raid not required RAID 0 RAID 0 + 1	When archiving logs, the archiving process may consume a lot of system resources, so the faster the better. If you use RAID 0 or do not use RAID, we recommend that you make several copies, if you use RAID 0 + 1, you can rest assured.
Rollback/Revocation Data Files	RAID 0 + 1	These files require constant I/O, and data needs to be protected, because Oracle cannot provide multiple copies of them, such as the control file, to provide more protection in the form of hardware, therefore, I recommend RAID 0 + 1.
Data Files	RAID 5 RAID 0 + 1	Most of the I/O operations on data files are performed in the cache, and physical write operations are performed in the background. Therefore, RAID 5 can reduce costs without affecting performance. We recommend that you use RAID 5, if I/O operations are performed frequently and RAID 5 feels slow, use RAID 0 + 1.

Some people may have doubts here. According to this design, how many hard disks are needed? Yes, to reduce maintenance time, enhance data security, and ensure application performance, A lot of hard disks are required to form raid in different forms. If you still have questions, the following are some principles that can be considered during space planning. For details, refer:

◆ If your budget is sufficient, you can store all Oracle files separately using RAID 0 + 1.
◆ To reduce costs, you can place data files on the RAID 5 array.
◆ If you want to reduce the cost, you can put all the data files on the RAID 5 array.
◆ If neither of them works, you can put the archived log files and rollback/Redo tablespace on the RAID 5 array.
◆ Finally, only RAID 5 can be used to store all files.