cluster – Page 2 – Technology Geek

Sometimes we need Solutions to keep our database Available all the time, There are lot of solutions one of these solutions called Oracle Real Application Cluster (RAC)/High Availability

As Lesson Number One i will take on Oracle Real Application Cluster Basics .

Lets Start :

Oracle RAC allows multiple computers to run Oracle RDBMS software simultaneously while accessing a single database, thus providing a clustered database.

In a non-RAC Oracle database, a single instance accesses a single database. The database consists of a collection of data files, control files, and redo logs located on disk. The instance comprises the collection of Oracle-related memory and operating system processes that run on a computer system.

In an Oracle RAC environment, two or more computers (each with an instance) concurrently access a single database. This allows an application or user to connect to either computer and have access to a single coordinated set of data.

Assume the installation of Oracle 10g release 2 (10.2) RAC on Red Hat Enterprise Linux 4.

Hardware
At the hardware level, each node in a RAC cluster shares three things:

Access to shared disk storage
Connection to a private network
Access to a public network.

Shared Disk Storage
Oracle RAC relies on a shared disk architecture. The database files, online redo logs, and control files for the database must be accessible to each node in the cluster. The shared disks also store the Oracle Cluster Registry and Voting Disk (discussed later). There are a variety of ways to configure shared storage including direct attached disks (typically SCSI over copper or fiber), Storage Area Networks (SAN), and Network Attached Storage (NAS).

Supported Shared Storage In RAC :

1-Oracle Cluster File System (OCFS) is a shared file system designed specifically for Oracle Real Application Cluster OCFS eliminates the requirement that Oracle database files be linked to logical drives and enables all nodes to share a single Oracle Home
2-ASM
3-RAW Device

Private Network
Each cluster node is connected to all other nodes via a private high-speed network, also known as the cluster interconnect or high-speed interconnect (HSI). This network is used by Oracle’s Cache Fusion technology to effectively combine the physical memory (RAM) in each host into a single cache. Oracle Cache Fusion allows data stored in the cache of one Oracle instance to be accessed by any other instance by transferring it across the private network. It also preserves data integrity and cache coherency by transmitting locking and other synchronization information across cluster nodes.
The private network is typically built with Gigabit Ethernet, but for high-volume environments, many vendors offer proprietary low-latency, high-bandwidth solutions specifically designed for Oracle RAC. Linux also offers a means of bonding multiple physical NICs into a single virtual NIC (not covered here) to provide increased bandwidth and availability.

Public Network
To maintain high availability, each cluster node is assigned a virtual IP address (VIP). In the event of node failure, the failed node’s IP address can be reassigned to a surviving node to allow applications to continue accessing the database through the same IP address.

Configuring the Cluster Hardware
There are many different ways to configure the hardware for an Oracle RAC cluster. Our configuration here uses two servers with two CPUs, 1GB RAM, two Gigabit Ethernet NICs, a dual channel SCSI host bus adapter (HBA), and eight SCSI disks connected via copper to each host (four disks per channel). The disks were configured as Just a Bunch Of Disks (JBOD)—that is, with no hardware RAID controller.

Software
At the software level, each node in a RAC cluster needs:

An operating system
Oracle Clusterware
Oracle RAC software
An Oracle Automatic Storage Management (ASM) instance (optional).

Operating System
Oracle RAC is supported on many different operating systems. This guide focuses on Linux. The operating system must be properly configured for the OS–including installing the necessary software packages, setting kernel parameters, configuring the network, establishing an account with the proper security, configuring disk devices, and creating directory structures. All these tasks are described in this guide.

Oracle Cluster Ready Services becomes Oracle Clusterware
Oracle RAC 10g Release 1 introduced Oracle Cluster Ready Services (CRS), a platform-independent set of system services for cluster environments. In Release 2, Oracle has renamed this product to Oracle Clusterware.
Clusterware maintains two files: the Oracle Cluster Registry (OCR) and the Voting Disk. The OCR and the Voting Disk must reside on shared disks as either raw partitions or files in a cluster filesystem. This guide describes creating the OCR and Voting Disks using a cluster filesystem (OCFS2) and walks through the CRS installation.

Oracle RAC Software
Oracle RAC 10g Release 2 software is the heart of the RAC database and must be installed on each cluster node. Fortunately, the Oracle Universal Installer (OUI) does most of the work of installing the RAC software on each node. You only have to install RAC on one node—OUI does the rest.

Oracle Automatic Storage Management (ASM) / Or other shared Storage .
ASM is a new feature in Oracle Database 10g that provides the services of a filesystem, logical volume manager, and software RAID in a platform-independent manner. Oracle ASM can stripe and mirror your disks, allow disks to be added or removed while the database is under load, and automatically balance I/O to remove “hot spots.” It also supports direct and asynchronous I/O and implements the Oracle Data Manager API (simplified I/O system call interface) introduced in Oracle9i.

Some Other Stuff you need To check Before Installation :

1-Crossover cables are not supported (use a high-speed switch).
2-Use at least a gigabit Ethernet for optimal performance.
3-Increase the UDP buffer sizes to the OS maximum.
4-Turn on UDP checksumming.
5-Oracle Support strongly recommends the use of UDP (TCP for WIndows )
6-SSH Connectivity .

Thank you
Osama mustafa

Today, all company needs to save data and information, these kinds of data different from company to other such as (pictures, employee and Customer data); it’s so rarely to find companies used papers to save important data.We don’t disagree on database type, Sure Oracle is the best but there’s another product in the market today such as Oracle, Microsoft and k2 but all these products have common thing Called Threats .

Before this, we need to know what we mean with database Security since it’s my article subject
Database Security: can be defined as a system or process by which the “Confidentiality, Integrity, and Availability (CIA) of the database can be protectedUnauthorized entry or access to a database server signifies a loss of confidentiality; unauthorized alteration to the available data signifies loss of integrity; and lack of access to database services signifies loss of availability. Loss of one or more of these basic facets will have a significant impact on the security of the database.
This is the common defined for database security.For an illustration of this concept, imagine that the website of a company contains information like who they are, what they do, and what prospective customers have to do to contact them for their queries. In this case, the availability of the database services is more important when compared with other factors like the confidentiality or integrity of the database security.
Threats and risks to databases have increased and therefore, the need for securing databases has also increased. When it comes to securing a database, lots of things have to take care of , if you was focused On pervious talking you will know that I am talking about:
1- Confidentiality
2- Integrity
3- Availability

Confidentiality

What I mean in this word is so simple by encrypting the data stored in the database,two type of encryption in database :
1-Data-in-transit:
This refers to data that is moving within the network. Sensitive data, for example, that is sent through network layers or through the Internet. A hacker can gain access to this sensitive data by eavesdropping. When this happens, the confidentiality of the data is compromised. Encrypting datain-transit avoids such compromises.

2- Data-at-rest:
It is possible for a hacker to hack the data that is stored in the database. Encrypting data-at-rest prevents such data leakages.

Integrity

I am not going to say it’s too simple to, because I don’t want from Listeners to kick me; but guys for me It’s simple sorry, Integrity talking about which users have to be given what permissions in the database For example, data related to employee information is stored in a database. An employee may have permission for viewing the records and altering only part of information like his contact details, whereas a person in the human resources department will have more privileges.

To make sure everything is going to be ok just following these steps:

Change the password, once the database is installed.

Policies to set strong passwords have to be enforced. A good idea is to have a policy of changing the passwords once per a month.

Does your company have multiple database administrators? If yes, segregate the duties
among these database administrators.

Simple steps (again simple) save you and your company.

Now last but I am not finished yet

Availability

Databases must not have unplanned downtime, to ensure this, following steps have to be taken:

To ensure high availability, usage of database clusters is recommended.
Databases should be secured against security vulnerabilities.
Backup the data at periodic intervals to ensure data recovery in case of application issues.

As we all know there’s nothing perfect so when we talk about Security, that mean we talk about Threats and attackers. With the increase in usage of databases, the frequency of attacks against those databases has also increased; Database attacks are an increasing trend these days. What is the reason behind database attacks? One reason is the increase in access to data stored in databases. When the data is been accessed by many people, the chances of data theft increases. In the past, database attacks were prevalent, but were less in number as hackers hacked the network more to show it was possible to hack and not to sell proprietary information. Another reason for database attacks is to gain money selling sensitive information, which includes credit card numbers, Social Security Numbers, etc. We previously defined database security and talked about common database security concepts. Now let’s look at the various types of threats that affect database security.

Thank You
Written By : Osama Mustafa
Consider this as part one since i will post another one related to this .
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Tag: cluster

Oracle Real Application Cluster Lesson # 1

Threats to Database Security Part 1