Topics: GPFS
View the GPFS nodes
Use the mmlsnode command to view the nodes in your GPFS nodesets:
# mmlsnode -a
Use the mmlsfs command to view the attributes and values of a GPFS file system. Use mmchfs to change the attributes of a GPFS file system. For example:
# mmlsfs /dev/slvdata01208
Use the mmlsdisk command to view the disks in a GPFS filesystem. Use the mmcrlv command to create GPFS volume groups and disks. For example:
# mmlsdisk /dev/slvdata01208
If a GPFS filesystem is changed (e.g. a disk error or caused by adding a disk) it is possible that a filesystem becomes no longer properly "balanced" or "replicated" (see the output of the mmlsdisk command). In GPFS 2.2 you could resolve this issue by running the mmrestripefs command. From GPFS 2.3 and onwards, the GPFS filesystems will balance themselves in a period of several weeks when data was changed. The messages about unbalanced file systems have disappeared in GPFS 3.2 alltogether. Because of this, do not run the mmrestripefs -b command on GPFS filesystems in GPFS 2.3. This may cause an unstable situation in which nodes could become unreachable.
A not properly replicated filesystem does need to be restriped however. Do this by running the mmrestripefs -r command.
WebSphere Application Server (WAS) is a server for deploying and managing applications on the web. It is a deployment environment for Java based applications (it is basically an environment for running Java code). For example, the eClient of IBM Content Manager uses Java Server Pages (JSPs). JSPs contain HTML and embedded Java code that is compiled and run by WAS, similar to PHP. WebSphere Application Server is actually part (or the foundation) of a huge range of products, called the WebSphere family of products.
WAS is built on the services of a web server to provide additional services to support business applications and transactions on the web. A common example of this is persistence support for user sessions that cannot be provided by only using an HTTP server. In general, WAS is able to facilitate a multi-tiered, web enabled environment that provides security, reliability, availability, scalability, flexibility and performance. WAS can, of course, serve static HTML and dynamic content.
Releases available:
- WAS Express (Single Server): Designed to support only a single hardware server. For small companies or individuals.
- WAS Base: intended for large production environments. Its purpose: A stand-alone, single machine, which is not scalable (1 process on 1 machine).
- WAS Network Deployment (ND): offers specific high end functionality. Actually the same as the base version, but this version is scalable: it can be spread over several systems to offer load-balancing capabilities.
- WAS Enterprise: the same as the ND version, but with added features. Nowadays it is also called the Business Integration Foundation version.
http://[server]:9090/adminWAS 5 has a connection pooling feature, which can result in a significant observable reduction in response time, especially for database connections. It reduces the overhead of creating a new connection for each user and disconnting it afterwards, by using existing connections from a connection pool. WAS communicates with databases via JDBC, which is actually the driver for a database.
First of all, start your HTTP Server and WAS administration server "server1".
In a browser, run the snoop servlet:
http://localhost:9080/snoopUsing port 9080 bypasses the web Server plug-in and uses the imbedded HTTP server of WebSphere Application Server.
In a browser, run the snoop servlet:
http://localhost/snoopThis uses port 80, which will test the Web Server plug-in of the HTTP Server, and the communication from the Web Server to WebSphere Application Server.
A number of external links, related to WebSphere Application Server:
Official IBM sites:
In file /var/mmfs/gen/mmsdrfs. In a cluster, one node is primary and another node is secondary cluster data server. For a GPFS change, both nodes need to be active. For starting a GPFS node, a least one of the two need to be active (but this is no problem, since GPFS doesn't work with only 1 node).
Use the mmlsconfig command to view which GPFS file systems are defined on your system.
The traditional method for making an Oracle database capable of 7*24 operation is by means of creating an HACMP cluster in an Active-Standby configuration. In case of a failure of the Active system, HACMP lets the standby system take over the resources, start Oracle and thus resumes operation. This takeover is done with a downtime period of aprox. 5 to 15 minutes, however the impact on the business applications is more severe. It can lead to interruptions up to one hour in duration.
Another way to achieve high availability of databases, is to use a special version of the Oracle database software called Real Application Cluster, also called RAC. In a RAC cluster multiple systems (instances) are active (sharing the workload) and provide a near always-on database operation. The Oracle RAC software relies on IBM's HACMP software to achieve high availability for hardware and the operating system platform AIX. For storage it utilizes a concurrent filesystem called GPFS (General Parallel File System), a product of IBM. Oracle RAC 9 uses GPFS and HACMP. With RAC 10 you no longer need HACMP and
GPFS.
HACMP is used for network down notifications. Put all network adapters of 1 node on a single switch and put every node on a different switch. HACMP only manages the public and private network service adapters. There are no standby, boot or management adapters in a RAC HACMP cluster. It just uses a single
hostname; Oracle RAC and GPFS do not support hostname take-over or IPAT (IP Address take-over). There are no disks, volume groups or resource groups defined in an HACMP RAC cluster. In fact, HACMP is only necessary for event handling for Oracle RAC.
Name your HACMP RAC clusters in such away, that you can easily recognize the cluster as a RAC cluster, by using a naming convention that starts with RAC_.
On every GPFS node of an Oracle RAC cluster a GPFS daemon (mmfs) is active. These daemons need to communicate with each other. This is done via the public network, not via the private network.
Cache Fusion
Via SQL*Net an Oracle block is read in memory. If a second node in an HACMP RAC cluster requests the same block, it will first check if it already has it stored locally in its own cache. If not, it will use a private dedicated network to ask if another node has the block in cache. If not, the block will be read from disk. This is called Cache Fusion or Oracle RAC interconnect.
This is why on RAC HACMP clusters, each node uses an extra private network adapter to communicate with the other nodes, for Cache Fusion purposes only. All other communication, including the communication between the GPFS daemons on every node and the communication from Oracle clients, is done via the public network adapter. The throughput on the private network adapter can be twice as high as on the public network adapter.
Oracle RAC will use its own private network for Cache Fusion. If this network is not available, or if one node is unable to access the private network, then the private network is no longer used, but the public network will be used instead. If the private network returns to normal operation, then a fallback to the private network will occur. Oracle RAC uses cllsif of HACMP for this purpose.
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