Another useful article on IBM developerworks shows how to build PHP extensions using SWIG. You can find the article here.
This article looks at the range of client access mechanisms for Windows that can be used with the Recital C-ISAM Bridge and details bridge configuration and usage.
Overview
Just because the format of data is regarded as 'legacy' does not make that data in any way obsolete. Modern client interfaces can not only extend the life of long-term data, but also provide different ways to analyse and gain advantage from that data.
Recital Corporation provides a range of solutions to interface to Informix compliant C-ISAM data on Linux or UNIX from Windows clients.
.NET
Click image to display full size
Fig 1: Recital Mirage .NET application accessing the C-ISAM Demo table.
Recital offers two alternative ways to access C-ISAM data using Microsoft .NET:
The Recital .NET Data Provider is a managed Data Provider written in C# that provides full compatibility with the Microsoft SQLserver and OLE DB data providers that ship with the .NET framework. It is fully integrated with the Visual Studio .NET IDE supporting data binding and automatic code generation using the form designer. The Recital .NET Data Provider works in conjunction with the Recital Database Server for Linux or UNIX to access C-ISAM data.
Recital Mirage .NET is a complete solution for migrating, developing and deploying 4GL database applications. Recital Mirage .NET works in conjunction with the Recital Mirage .NET Application Server for Linux or UNIX to access C-ISAM data.
JDBC
Click image to display full size
Fig 2: Java™ Swing JTable accessing the C-ISAM Demo table via the Recital JDBC Driver.
The Recital JDBC Driver is an all Java Type 4 JDBC 3.0 Driver, allowing you to access C-ISAM data from Java applets and applications. The Recital JDBC Driver works in conjunction with the Recital Database Server for Linux or UNIX to access C-ISAM data.
ODBC
Click image to display full size
Fig 3: Microsoft® Office Excel 2003 Pivot Chart and Pivot Table accessing the C-ISAM Demo table via the Recital ODBC Driver.
The Recital ODBC Driver is an ODBC 3.0 Driver, allowing you to access C-ISAM data from your preferred ODBC based Windows applications. You can develop your own applications in languages such as C++ or Visual Basic, manipulate the data in a spreadsheet package or word processor document and design charts, graphs and reports. The Recital ODBC Driver works in conjunction with the Recital Database Server for Linux or UNIX to access C-ISAM data.
Configuring the Recital C-ISAM Bridge
Data access is achieved through a C-ISAM Bridge. This requires the creation of an empty Recital table that has the same structure as the C-ISAM file and of a RecitalC-ISAM Bridge file.
On Linux and UNIX, Recital Terminal Developer and the Recital Database Server come complete with an example C-ISAM data file, C-ISAM index and Recital C-ISAM bridge that can be used for testing and as a template for configuring your own C-ISAM bridges. The Recital Database Server also includes a bridge creation ini file.
Step 1:
Create a Recital table with the same structure as the C-ISAM file. The fields/columns in the structure file must exactly match the data type and length of those in the C-ISAM file. The Recital table will have one byte more in total record length due to the Recital record deletion marker.
To create the table, use the SQL CREATE TABLE command or the Recital Terminal Developer CREATE worksurface. The SQL CREATE TABLE command can be called directly:
SQLExecDirect:
In: hstmt = 0x00761BE8,
szSqlStr = "CREATE TABLE cisamdemo.str (DD Char(4)
DESCRIPTION "Dd...", cbSqlStr = -3
Return: SQL_SUCCESS=0
or be included in a 4GL program:
// createtab.prg
CREATE TABLE cisamdemo.str;
(DD Char(4) DESCRIPTION "Dd",;
CONFIRM Char(6) DESCRIPTION "Confirm",;
PROCDATE Char(6) DESCRIPTION "Procdate",;
CONTROL Char(5) DESCRIPTION "Control",;
DOLLARS Decimal(13,2) DESCRIPTION "Dollars",;
DEALER Char(5) DESCRIPTION "Dealer",;
TERRITORY Char(2) DESCRIPTION "Territory",;
WOREP Char(12) DESCRIPTION "Worep",;
CURRTRAN Char(3) DESCRIPTION "Currtran",;
TRADDATE Char(6) DESCRIPTION "Traddate",;
CITY Char(10) DESCRIPTION "City",;
ACCOUNT Char(11) DESCRIPTION "Account",;
PRETRAN Char(2) DESCRIPTION "Pretran",;
AFSREP Char(14) DESCRIPTION "Afsrep",;
REPKEY Char(9) DESCRIPTION "Repkey",;
BRANCH Char(3) DESCRIPTION "Branch",;
WODEALER Char(5) DESCRIPTION "Wodealer",;
BANKCODE Char(2) DESCRIPTION "Bankcode",;
COMMRATE Decimal(6,4) DESCRIPTION "Commrate",;
NEWREP Char(1) DESCRIPTION "Newrep",;
SETTLE Char(1) DESCRIPTION "Settle",;
POSTDATE Char(6) DESCRIPTION "Postdate")
if file("cisamdemo.str")
return .T.
else
return .F.
endif
// end of createtab.prg
Server-side 4GL programs can be called by all clients, e.g. from a Java class with a JDBC connection:
//---------------------------------
//-- create_str.java --
//---------------------------------
import java.sql.*;
import java.io.*;
import Recital.sql.*;
public class create_str {
public static void main(String argv[]) {
try {
new RecitalDriver();
String url = "jdbc:Recital:" +
"SERVERNAME=cisamserver;" +
"DIRECTORY=/usr/recital/data/southwind;" +
"USERNAME=user;" +
"PASSWORD=password";
Connection con = DriverManager.getConnection(url, "user", "pass");
Statement stmt = con.createStatement();
CallableStatement sp = con.prepareCall("{call createtab}");
boolean res = sp.execute();
String outParam = sp.getString(1);
System.out.println("Returned "+outParam);
sp.close();
con.close();
} catch (Exception e) {
System.out.flush();
System.err.flush();
DriverManager.println("Driver exception: " + e.getMessage());
e.printStackTrace();
}
try {
System.out.println("Press any key to continue...");
System.in.read();
} catch(IOException ie) {
;
}
}
}
The table should be given a ‘.str’ file extension (rather than the default ‘.dbf’) to signify that this is a structure file only.
Please see the end of this article for information on matching Informix and Recital data types
Fig 4: Recital CREATE/MODIFY STRUCTURE worksurface for character mode table creation.
Step 2: Creating the Bridge File
If you have Recital installed on the server platform, the Bridge File can be created using the CREATE BRIDGE worksurface. The corresponding command to modify the bridge file is MODIFY BRIDGE <bridge file>. This is the cisamdemo.dbf bridge file in the CREATE/MODIFY BRIDGE WORKSURFACE:
> modify bridge cisamdemo.dbf
Fig 5: Recital CREATE BRIDGE/MODIFY BRIDGE worksurface for bridge creation.
For Recital Database Server clients, the Bridge File can be created using the Recital/SQL CREATE BRIDGE command:
Recital/SQL CREATE BRIDGE:
CREATE BRIDGE cisamdemo.dbf; TYPE "CISAM"; EXTERNAL "cisamdemo.dat"; METADATA "cisamdemo.str"; ALIAS "cisamdemo"
or:
CREATE BRIDGE cisamdemo.dbf; AS "type=CISAM;external=cisamdemo.dat;metadata=cisamdemo.str;alias=cisamdemo"
The examples above assume that the C-ISAM file, the bridge file and the Recital structure file are all in the current working directory. Full path information can be specified for the <externalname> and the <databasename>. For added flexibility, environment variables can be used to determine the path at the time the bridge is opened. Environment variables can be included for either or both the <externalname> and the <databasename>. A colon should be specified between the environment variable and the file name.
e.g.
CREATE BRIDGE cisamdemo.dbf; TYPE "CISAM"; EXTERNAL "DB_DATADIR:cisamdemo"; METADATA "DB_MIRAGE_PATH:cisamdemo.str"; ALIAS "cisamdemo"
Recital CREATE BRIDGE/MODIFY BRIDGE worksurface:
Fig 6: Recital CREATE BRIDGE/MODIFY BRIDGE worksurface - using environment variables.
Using the Bridge
The Bridge can now be used. To access the C-ISAM file, use the ‘alias’ specified in the Bridge definition.
SQL:
SELECT * FROM cisamdemo
Recital/4GL:
use cisamdemo
Indexes
The cisamdemo.dat file included in the Recital distributions for Linux and UNIX has three associated index keys in the cisamdemo.idx file:
Select area: 1 Database in use: cisamdemo Alias: cisamdemo Number of records: 4 Current record: 2 File Type: CISAM (C-ISAM) Master Index: [cisamdemo.idx key #1] Key: DD+CONFIRM+PROCDATE+CONTROL Type: Character Len: 21 (Unique) Index: [cisamdemo.idx key #2]
Key: DD+SUBSTR(CONFIRM,2,5)+TRADDATE+STR(DOLLARS,13,2) +CURRTRAN+ACCOUNT Type: Character Len: 42 Index: [cisamdemo.idx key #3] Key: DEALER+BRANCH+AFSREP+SUBSTR(PROCDATE,5,2) +SUBSTR(CONTROL,2,4) Type: Character Len: 28
The Recital C-ISAM bridge makes full use of the C-ISAM indexes. SQL SELECT statements with WHERE clauses are optimized based on any of the existing indexes when possible. The following ODBC SELECT call makes use of key #3 rather than sequentially searching through the data file.
SQLExecDirect:
In: hstmt = 0x00761BE8,
szSqlStr = "select * from cisamdemo
where dealer+branch+afsrep=' 00161 595-7912",
cbSqlStr = -3
Return: SQL_SUCCESS=0
Get Data All:
"DD", "CONFIRM", "PROCDATE", "CONTROL", "DOLLARS", "DEALER",
"TERRITORY", "WOREP", "CURRTRAN", "TRADDATE", "CITY", "ACCOUNT",
"PRETRAN", "AFSREP", "REPKEY", "BRANCH", "WODEALER", "BANKCODE",
"COMMRATE", "NEWREP", "SETTLE", "POSTDATE"
"0159", " 15522", "930312", "13356", 4992.60, "00161", "19",
"", "210", "930305", "", "70000100009", "", "595-7912",
"930315791", "", "", "59", 0.0000, "1", "", "930315"
1 row fetched from 22 columns.
Using the Recital/4GL, the primary index is set as the master index when the bridge is first opened. Any secondary indexes can be selected using the SET ORDER TO <expN> command. The Recital/4GL SEEK or FIND commands and SEEK() function can be used to search in the current master index.
> SET ORDER TO 3 Master index: [cisamdemo.idx key #3] > SEEK “00161 595-7912”
Appendix 1: Data Types
|
Informix |
Recital |
|
Byte |
Numeric |
|
Char |
Character |
|
Character |
Character |
|
Date |
Date |
|
Datetime |
Character |
|
Decimal |
Numeric |
|
Double Precision |
Float |
|
Float |
Real |
|
16 Bit Integer |
Short |
|
Integer |
Numeric |
|
Interval |
Character |
|
32 Bit Long |
Integer |
|
Money |
Numeric |
|
Numeric |
Numeric |
|
Real |
Numeric |
|
Smallfloat |
Numeric |
|
Smallint |
Numeric |
|
Text |
Unsupported |
|
Varchar |
Character |
Appendix 2: C-ISAM RDD Error Messages
The following errors relate to the use of the Recital CISAM Replaceable Database Driver (RDD). They can be received as an ‘errno <expN>’ on Recital error messages:
|
ERRNO() |
Error Description |
|
100 |
Duplicate record |
|
101 |
File not open |
|
102 |
Invalid argument |
|
103 |
Invalid key description |
|
104 |
Out of file descriptors |
|
105 |
Invalid ISAM file format |
|
106 |
Exclusive lock required |
|
107 |
Record claimed by another user |
|
108 |
Key already exists |
|
109 |
Primary key may not be used |
|
110 |
Beginning or end of file reached |
|
111 |
No match was found |
|
112 |
There is no “current” established |
|
113 |
Entire file locked by another user |
|
114 |
File name too long |
|
115 |
Cannot create lock file |
|
116 |
Memory allocation request failed |
|
117 |
Bad custom collating |
|
118 |
Duplicate primary key allowed |
|
119 |
Invalid transaction identifier |
|
120 |
Exclusively locked in a transaction |
|
121 |
Internal error in journaling |
|
122 |
Object not locked |
There is a good article on the gluster website here which gives some good information regarding file system optimization suitable for a HA Recital cluster solution.
In this article Chris Mavin, explains and details how to use the Recital Database Server with the Open Source Servlet Container Apache Tomcat.
Overview
PHP has exploded on the Internet, but its not the only way to create web applications and dynamic websites. Using Java Servlets, JavaServer Pages and Apache Tomcat you can develop web applications in a more powerful full featured Object Oriented Language, that is easier to debug, maintain, and improve.
Tomcat Installation
There are a number of popular Java application servers such as IBM Web Sphere and BEA WebLogic but today we will be talking about the use of Apache Tomcat 5, the Open Source implementation of the Java Servlet and JavaServer Pages technologies developed at the Apache Software Foundation. The Tomcat Servlet engine is the official reference implementation for both the Servlet and JSP specifications, which are developed by Sun under the Java Community Process. What this means is that the Tomcat Server implements the Servlet and JSP specifications as well or better than most commercial application servers.
Apache Tomcat is available for free but offers many of the same features that commercially available Web application containers boast.
Tomcat 5 supports the latest Servlet and JSP specifications, Servlet 2.4, and JSP 2.0, along with features such as:
-
Tomcat can run as a standalone webserver or a Servlet/JSP engine for other Web Servers.
-
Multiple connectors - for enabling multiple protocol handlers to access the same Servlet engine.
-
JNDI - The Java Naming and Domain Interface is supported.
-
Realms - Databases of usernames and passwords that identify valid users of a web application.
-
Virtual hosts - a single server can host applications for multiple domain names. You need to edit server.xml to configure virtual hosts.
-
Valve chains.
-
JDBC - Tomcat can be configured to use any JDBC driver.
-
DBCP - Tomcat can use the Apache commons DBCP for connection pooling.
-
Servlet reloading (Tomcat monitors any changes to the classes deployed within that web server.)
-
HTTP functionality - Tomcat functions as a fully featured Web Server.
-
JMX, JSP and Struts-based administration.
Tomcat Installation
In this next two sections we will walk through the install and setup of Tomcat for use with the Recital database server.
To download Tomcat visit the Apache Tomcat web site is at http://jakarta.apache.org/tomcat.
Follow the download links to the binary for the hardware and operating system you require.
For Tomcat to function fully you need a full Java Development Kit (JDK). If you intend to simply run pre compiled JavaServer pages you can do so using just the Java Runtime Environment(JRE).
The JDK 1.5 is the preferred Java install to work with Tomcat 5, although it is possible to run Tomcat 5 with JDK 1.4 but you will have to download and install the compat archive available from the Tomcat website.
For the purpose of this article we will be downloading and using Tomcat 5 for Linux and JDK 5.0,
you can download the JDK at http://java.sun.com/javase/downloads/index.jsp.
Now we have the JDK, if the JAVA_HOME environment variable isn't set we need to set it to refer to the base JDK install directory.
Linux/Unix:
$ JAVA_HOME= /usr/lib/j2se/1.4/ $ EXPORT $JAVA_HOME
Windows NT/2000/XP:
Follow the following steps:
1. Open Control Panel.
2. Click the System icon.
3. Go to the Advanced tab.
4. Click the Environment Variables button.
5. Add the JAVA_HOME variable into the system environment variables.
The directory structure of a Tomcat installation comprises of the following:
/bin - Contains startup, shutdown and other scripts. /common - Common classes that the container and web applications can use. /conf - Contains Tomcat XML configuration files XML files. /logs - Serlvet container and application logs. /server - Classes used only by the Container. /shared - Classes shared by all web application. /webapps - Directory containing the web applications. /work - Temporary directory for files and directories.
The important files that you should know about are the following:
-
server.xml
The Tomcat Server main configuration file is the [tomcat install path]\conf\server.xml file. This file is mostly setup correctly for general use. It is within this file where you specify the port you wish to be running the server on. Later in this article I show you how to change the default port used from 8080 to port 80.
-
web.xml
The web.xml file provides the configuration for your web applications. There are two locations where the web.xml file is used,
web-inf\web.xml provides individual web application configurations and [tomcat install path]conf\web.xml contains the server wide configuration.
Setting up Tomcat for use
We'll start by changing the port that Tomcat will be listening on to 80.
To do this we need to edit [tomcat install path]/conf/server.xml and change the port attribute of the connector element from 8080 to 80.
After you have made the alteration the entry should read as:
<!-- Define a non-SSL HTTP/1.1 Connector on port 8080 --> <Connector port="80" maxHttpHeaderSize="8192"
Next we want to turn on Servlet reloading, this will cause the web application to be recompiled each time it is accessed, allowing us to make changes to the files without having to worry about if the page is being recompiled or not.
To enable this you need to edit [tomcat install path]/conf/context.xml and change <Context> element to <Context reloadable="true">.
After you have made the alteration the entry should read as:
<Context reloadable="true"> <WatchedResource>WEB-INF/web.xml</WatchedResource> </Context>
Next we want to enable the invoker Servlet.
The "invoker" Servlet executes anonymous Servlet classes that have not been defined in a web.xml file. Traditionally, this Servlet is mapped to the URL pattern "/servlet/*", but you can map it to other patterns as well. The extra path info portion of such a request must be the fully qualified class name of a Java class that implements Servlet, or the Servlet name of an existing Servlet definition.
To enable the invoker Servlet you need to edit the to [tomcat install path]/conf/web.xml and uncomment the Servlet and Servlet-mapping elements that map the invoker /servlet/*.
After you have made the alteration the entry should read as:
<servlet> <servlet-name>invoker</servlet-name> <servlet-class>org.apache.catalina.servlets.InvokerServlet</servlet-class> <init-param> <param-name>debug</param-name> <param-value>0</param-value> </init-param> <load-on-startup>2</load-on-startup> </servlet> <servlet-mapping> <servlet-name>invoker</servlet-name> <url-pattern>/servlet/*</url-pattern> </servlet-mapping>
If you are you not interested in setting up your own install of Tomcat there are prebuilt versions Tomcat that has all of the above changes already made, and has the test HTML, JSP, and Servlet files already bundled. Just unzip the file, set your JAVA_HOME
Next we will give Tomcat and your web applications access to the Recital JDBC driver.
For the purposes of this article we are going to install the Recital JDBC driver in the /[tomcat install path]/common/lib/ this gives Tomcat and your web applications access to the Recital JDBC driver. The driver can be installed in a number of places in the Tomcat tree, giving access to the driver to specific application or just to the web application and not the container. For more information refer to the Tomcat documentation.
Copy the recitalJDBC.jar which is located at /[recital install path]/drivers/recitalJDBC.jar to the /[tomcat install path]/common/lib/ directory.
Linux:
$cp /[recital install path]/drivers/recitalJDBC.jar /[tomcat install path]/common/lib/
Once you have completed all the steps detailed above, fire up the server using the script used by your platform's Tomcat installation.
Linux/Unix:
[tomcat install path]/bin/startup.sh
Windows:
[tomcat install path]/bin/startup
If you are having problems configuring your Tomcat Installation or would like more detail visit the online documentation a the Apache Tomcat site.
Example and Links
Now we have setup our Tomcat installation, lets get down to it with a JSP example which uses the Recital JDBC driver to access the demonstration database (southwind) shipped with the Recital Database Server.
The example provided below is a basic JDBC web application, where the user simply selects a supplier from the listbox and requests the products supplied by that supplier.
To run the example download and extract the tar archive or simple save each of the two jsp pages individually into /[tomcat install path]/webapps/ROOT/ on your server.
By enabling the invoker Servlet earlier we have removed the need to set the example up as a web application in the Tomcat configuration files.
You can now access the example web application at http://[Server Name]/supplier.jsp if the page doesn't display, check you have followed all the Tomcat installation steps detailed earlier in this article and then make sure both Tomcat and a licensed Recital UAS are running.
Downloads:
Archive: jspExample.tar
Right click and save as individual files and rename as .jsp files:
supplier.txt details.txt
Further Reading on JSP and JDBC can be found at http://www-128.ibm.com/developerworks/java/library/j-webdata/
Final Thoughts
Recital and Apache tomcat are a powerful combination, using Java Servlet technology you can separate application logic and the presentation extremely well. Tomcat, JSP, Java Servlets and the Recital database server form a robust platform independent, easily maintained and administered solution with which to unlock the power of your Recital, Foxpro, Foxbase, Clipper, RMS and C-SAM data.
In this article Barry Mavin explains step by step how to setup a Linux HA (High Availability) cluster for the running of Recital applications on Redhat/Centos 5.3 although the general configuration should work for other linux versions with a few minor changes.
I am a fan of the previous incarnation of the PlugComputer so I was excited to see that Marvell have unveiled a new PlugComputer dubbed imaginatively "PlugComputer 3.0."
PlugComputer 3.0 Features:
Smaller sleeker design,
More powerful CPU - 2gz Armanda 300 CPU,
120GB 1.8-inch SATA hard drive,
Wifi,
Bluetooth,
10/100/1000 wired Ethernet,
USB 2.0.
512MB of RAM
512MB of Flash memory
I for one would like to see an additional Ethernet port added to increase application flexibility, for some applications where you are using clustered plugs or even for routing, having multiple Ethernet ports is a must.
Even without multiple ethernet ports, these low power consumption devices really could have a place in SME environments, replacing large cumbersome legacy hardware with compact Linux plug servers.
More information about the PlugComputer can be found here
Here's how to set up field validation based on dynamic values from another table.
Using the products.dbf table from the southwind sample database, validation can be added to the categoryid field to ensure it matches an existing categoryid from the categories.dbf table.
open database southwindThe rlookup() function checks whether an expression exists in the index (master or specified) of the specified table . An attempt to update categoryid with a value not in the list will give an error: Validation on field 'CATEGORYID' failed.
alter table products add constraint;
(categoryid set check rlookup(products.categoryid,categories))
If you have access to the Recital Workbench, you can use the modify structure worksurface to add and alter your dictionary entries, including a customized error message if required.
If you are running your Redhat/Centos or Fedora machine in an enterprise environment you may be sitting behind a network proxy server like squid.
If you try and update or install software it will fail with timeouts or errors contacting the repository mirrors.
To configure YUM to work with your proxy server you need to add the following line to your /etc/yum.conf file.
Anonymous proxy configuration:
proxy=http://yourproxyip:port/
If your proxy server requires authentication add the following lines to your /etc/yum.conf file instead.
proxy=http://yourproxyip:port/ proxy_username=youruser proxy_password=yourpassword
You will be able to update and install software now, give it a go!
DRBD:
DRBD (Distributed Replicated Block Device) forms the storage redundancy portition of a HA cluster setup. Explained in basic terms DRBD provides a means of achieving RAID 1 behavoir over a network, where whole block devices are mirrored accross the network.
To start off you will need 2 indentically sized raw drives or partitions. Many how-to's on the internet assume the use of whole drives, of course this will be better performance, but if you are simply getting familar with the technology you can repartition existing drives to allow for two eqaully sized raw partitions, one on each of the systems you will be using.
There are 3 DRBD replication modes:
• Protocol A: Write I/O is reported as completed as soon as it reached local disk and local TCP send buffer
• Protocol B: Write I/O is reported as completed as soon as it reached local disk and remote TCP buffer cache
• Protocol C: Write I/O is reported as completed as soon as it reached both local and remote disks.
If we were installing the HA cluster on a slow LAN or if the geogrphical seperation of the systems involved was great, then I recommend you opt for asyncronous mirroring (Protocol A) where the notifcation of a completed write operation occurs as soon as the local disk write is performed. This will greatly improve performance.
As we are setting up our HA cluster connected via a fast LAN, we will be using DRBD in fully syncronous mode, protocol C.
Protocol C involves the file system on the active node only being notified that the write operation was finished when the block is written to both disks of the cluster. Protocol C is the most commonly used mode of DRBD.
/etc/drbd.conf
global { usage-count yes; }
common { syncer { rate 10M; } }
resource r0 {
protocol C;
net {
max-buffers 2048;
ko-count 4;
}
on bailey {
device /dev/drbd0;
disk /dev/sda4;
address 192.168.1.125:7789;
meta-disk internal;
}
on giskard {
device /dev/drbd0;
disk /dev/sda3;
address 192.168.1.127:7789;
meta-disk internal;
}
}
drbd.conf explained:
Global section, usage-count. The DRBD project keeps statistics about the usage of DRBD versions. They do this by contacting a HTTP server each time a new DRBD version is installed on a system. This can be disabled by setting usage-count no;.
The common seciton contains configurations inhereted by all resources defined.
Setting the syncronisation rate, this is accoimplished by going to the syncer section and then assigning a value to the rate setting. The syncronisation rate refers to rate in which the data is being mirrored in the background. The best setting for the syncronsation rate is related to the speed of the network with which the DRBD systems are communicating on. 100Mbps ethernet supports around 12MBps, Giggabit ethernet somewhere around 125MBps.
in the configuration above, we have a resource defined as r0, the nodes are configured in the "on" host subsections.
"Device" configures the path of the logical block device that will be created by DRBD
"Disk" configures the block device that will be used to store the data.
"Address" configures the IP address and port number of the host that will hold this DRBD device.
"Meta-disk" configures the location where the metadata about the DRBD device will be stored.
You can set this to internal and DRBD will use the physical block device to store the information, by recording the metadata within the last sections of the disk.
Once you have created your configuration file, you must conduct the following steps on both the nodes.
Create device metadata.
$ drbdadm create-md r0
v08 Magic number not found
Writing meta data...
initialising activity log
NOT initialized bitmap
New drbd meta data block sucessfully created.
success
Attach the backing device.
$ drbdadm attach r0
Set the syncronisation parameters.
$ drbdadm syncer r0
Connect it to the peer.
$ drbdadm connect r0
Run the service.
$ service drbd start
Heartbeat:
Heartbeat provides the IP redundancy and the service HA functionailty.
On the failure of the primary node the VIP is assigned to the secondary node and the services configured to be HA are started on the secondary node.
Heartbeat configuration:
/etc/ha/ha.conf
## /etc/ha.d/ha.cf on node1
## This configuration is to be the same on both machines
## This example is made for version 2, comment out crm if using version 1
// replace the node variables with the names of your nodes.
crm no
keepalive 1
deadtime 5
warntime 3
initdead 20
bcast eth0
auto_failback yes
node bailey
node giskard
/etc/ha.d/authkeys
// The configuration below set authentication off, and encryption off for the authentication of nodes and their packets.
//Note make sure the authkeys file has the correct permisisions chmod 600
## /etc/ha.d/authkeys
auth 1
1 crc
/etc/ha.d/haresources
//192.168.1.40 is the VIP (Virtual IP) assigned to the cluster.
//the "smb" in the configuration line represents the service we wish to make HA
// /devdrbd0 represents the resource name you configured in the drbd.conf
## /etc/ha.d/haresources
## This configuration is to be the same on both nodes
bailey 192.168.1.40 drbddisk Filesystem::/dev/drbd0::/drbdData::ext3 smb