Home > Articles > Programming > General Programming/Other Languages

  • Print
  • + Share This
Like this article? We recommend

Best Practices

The differential analysis in the preceding section leads to the following general rules for maintaining a highly available Sun Cluster environment. These rules have implications both for software designers of high-availability systems, as well as for people who maintain the high-availability environment of a deployed system. The rules relate to the top four parameters identified in the differential analysis in the preceding section.

  • Rule 1: If there is a node failure, minimize the probability of unsuccessful reconfiguration, thus improving p.

  • Rule 2: Minimize single node failures, thus increasing MTBF.

  • Rule 3: If there is an unsuccessful reconfiguration (leading to the entire cluster going down) minimize the time taken to bring the cluster back up, thus decreasing MTTR_2.

  • Rule 4: In case of successful reconfiguration, minimize the outage duration, thus decreasing Recovery_Time.

These rules are used while designing high-availability software such as the Sun Cluster software product, which aims to minimize service outage. However, it is well-known that failures in complex systems are due not only to hardware and software problems, but also to people and process issues8. A recent Boeing study9 reported that, of the fatal commercial aircraft incidents between 1959 and 2001, people/process caused 72 percent, with environment (weather) and equipment causing the remaining ones.

A set of best practices (BPs) can be derived from the rules stated previously. These BPs can be used towards minimizing the impact of people and process on the availability offered by the Sun Cluster software product. There are several projects underway at Sun that are collecting data for finding the root cause of specific cluster failures, or for configuration-related failures, to mention a few. Analyses of this data as well as the experience of several field engineers working closely with the Sun Cluster software product, have resulted in a wealth of information regarding the root causes of a multitude of cluster failure scenarios. This information, together with the rules developed previously, leads to a set of BPs, which are listed below. This set is not complete by any means, and must be augmented on a continuing basis. It also does not necessarily represent the top ten BPs, but is instead based on the frequency of failures seen by the data collection efforts mentioned previously.

Most of the following BPs are generic in nature, applying to any Sun Cluster stack; the last two are specific to the two-node RAC stack discussed in "The Stack." Additionally, some of these BPs are specific to the installation phase, some others are specific to the operational phase, and the remaining apply to both phases:

  1. BP1: Carefully plan the installation. Planning an installation carefully includes (but is not limited to) the following steps:

    1. Document the cluster configuration.

    2. Ensure consistent configurations across nodes and services.

    3. Clearly identify and label all devices and cables.

    4. Minimize single points of failure with straightforward designs, distributing cabling and connections across multiple system boards, and IO cards.

    5. Configure fewer active components, in a simple and consistent manner.

    6. Ensure cluster design conforms to vendor support guidelines.

    Sun has several customized programs of various costs, scaled to suit different customer install needs, that will facilitate a smooth installation. Getting the install right is critical in preventing future downtime due to a vulnerable configuration, and enables quick and consistent recovery operations. BP1 relates to rules 1 and 3.

  2. BP2: Install the latest required Solaris OE patches, rebooting the system after patches have been installed and applied.

    Ensure that all firmware is installed with the most recent, required versions for all systems and subsystems.

    The latest firmware and software versions and patches have fixes for known problems and bugs. Installing these helps to improve the MTBF of each cluster node. It also decreases the chances of an unsuccessful reconfiguration due to known and fixed bugs in the software and/or firmware code, and could potentially decrease recovery time depending on the fixes in the latest revision. After nodes are rebooted, cluster membership needs to be verified to contain the expected members. BP2 relates to rules 1, 2 and 4.

    Since this process requires a node outage, care should be taken to ensure rapid recovery to the Both_Up state. Policies regarding patch application vary widely between sites. This recommendation is not intended to change accepted policies nor is it intended to bypass the due diligence for patch analysis.

  3. BP3: Perform a complete acceptance test before placing a cluster into its production mode.

    A complete acceptance test includes burn-in of nodes with SunVTS and STORtools; development of thorough installation verification procedures; detailed tests with expected outcomes and times for common outages such as failover; and running a real client during testing to verify that service migration (via failover or switchover) works as expected. This is discussed in more detail in "Accelerate RAS into your Data Center",10 in the context of a specific clustering environment deploying 50 HA-NFS clusters at Sun. BP3 relates to rules 1, 2, 3 and 4.

  4. BP4: Perform periodic auditing of the cluster hardware and software components.

    We strongly recommend that all components of a cluster be audited periodically, including hardware and software components from Sun as well as any from third party vendors that form the stack in question. Configuration errors on cluster nodes can lead to a node failure, or the entire cluster failure, or the service not being started on a given node in the cluster after a reconfiguration. Several tools are available to facilitate regular monitoring of cluster components. The sccheck command that is part of the base Sun Cluster software has a set of useful checks currently, and is being augmented with several more. Also, Sun is expanding its products and service offerings to include additional proactive and preemptive support of the same. Certain contract levels provide regular access to reports that may help identify potential vulnerabilities in the system. Auditing is also discussed in some detail in "Accelerate RAS into your Data Center",10. BP4 relates to rules 1, 2, and 3.

  5. BP5: Repair failed components promptly.

    Although the failure of components can be transparent (causing no outage) or can be recoverable (causing a failover), the remaining redundant components that have taken over the service are essentially operating in a degraded mode, such that the cluster may not survive the next failure. So it is critical to repair the failed components, thus getting the cluster out of its degraded state. BP5 relates to rule 3.

  6. BP6: Applications running on the cluster and consisting of real-time (RT) processes or threads, should be well-behaved.

    The reconfiguration sequence in the Sun Cluster framework relies on the timely processing of the reconfiguration activities. This implies that any application RT threads running on the cluster nodes must be well-behaved, that is, those threads should not monopolize system resources. Otherwise, the reconfiguration threads will not run in a timely fashion. This can lead to timeouts resulting in unsuccessful reconfigurations, and nodes (or even the entire cluster) going down. Several instances of misbehaving application RT processes have been seen in the field. In these cases, the RT processes have monopolized system resources, causing timeouts and leading to cluster deadlocks or node failures.

    Note that this requirement is a basic Solaris OE requirement regarding well-behaved RT processes/threads; however, non-conformance to it does exacerbate the cluster reconfiguration steps and decreases availability in a clustering environment. BP6 relates to rules 1, 2 and 4.

  7. BP7: Periodically check any quorum devices configured in the cluster.

    Although this is part of BP4, it is called out separately since it has consequences that are significantly critical to successful reconfigurations. This BP is particularly relevant in two-node clusters, which are required to have a quorum device configured. In such clusters, if a node goes down, the remaining node would not be able to continue if it could not access the quorum device for any reason. This issue also applies to larger clusters with quorum devices, although the final impact of a failed quorum device depends on the number of nodes remaining up and other quorum devices in the cluster. BP7 relates to rule 1.

  8. BP8: Ensure (by periodically checking) that all third party licenses needed by the service in question remain valid.

    This BP is necessary to prevent any potential outages in the cluster due to missing or expired licenses on the nodes when a reconfiguration occurs in the cluster. Taking the example of the stack presented in "The Stack," Veritas VxVM requires its own license and these licenses may come with an expiration time or may be tied to the hostid of a node. If, at the time of a reconfiguration, the license has expired or the hostid has changed, the remaining cluster nodes will be forced to go down due to an unsuccessful reconfiguration. BP8 relates to rule 1.

  9. BP9: For the Sun Cluster-RAC on VxVM stack considered in this paper, configure the RAC storage layout as follows: use HW RAID-5 for RAC data, and striped RAID-0 with hardware or software mirroring for the RAC logs.

    RAID-5 can tolerate a single spindle failure and it performs well for random writes. However, it does not perform as well for sequential writes. On the other hand, using striping with mirroring performs well for sequential writes, but the recovery time can be quite large in the event of a spindle failure. The typical size of RAC data is orders of magnitude larger than the size of RAC logs. This coupled with the fact that logs are characterized by sequential writes, leads to the recommendation of using striped RAID-0 for RAC logs, and RAID-5 for RAC data. BP9 relates to rule 3.

    In general, a good match between the storage configuration and data access patterns, while maintaining high storage reliability, is recommended.

  10. BP10: For the Sun Cluster and Oracle9i RAC on VxVM stack, use the Veritas SmartSync feature for the RAC data, and use dirty region logging (DRL) for the logs.

    The SmartSync feature of VxVM offers increased availability of Oracle volumes by eliminating the need for the volume manager to perform resynchronization of the data volumes. Instead, VxVM relies on the Oracle recovery process to rewrite any potentially out-of-sync data blocks, thereby significantly reducing the recovery times. This feature is available for use only for Oracle9i RAC data. For the RAC logs, the DRL option of VxVM should be used to improve log related recovery performance. BP10 relates to rules 3 and 4.

  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020