HP serviceguard t2808-90006 manual Cluster Reformation Time and Timeout Values

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Configuring your Environment for Software RAID

Configuring Multiple Paths to Storage

The QLogic cards are configured to hold up any disk access and essentially hang for a time period which is greater than the cluster reformation time when access to a disk is lost. This is achieved by altering the Link Down Timeout value for each port of the card. Setting a value for the Link Down Timeout parameter for a QLogic card ensures that the MD device hangs when access to a mirror is lost. For configurations with multipath, the MD device hangs when one path to a storage system is lost. However, the MD device resumes activity when the specified hang period expires. This ensures that no data is lost.

This parameter is required to address a scenario where an entire datacenter fails but all its components do not fail at the same time but undergo a rolling failure. In this case, if the access to one disk is lost, the MD layer hangs and data is no longer written to it. Within the hang period, the node goes down and a cluster reformation takes place. When the package fails over to another node, it starts with a disk that has current data.

The value to be set for Link Down Timeout parameter depends on the heartbeat interval and the node timeout values configured for a particular cluster. Use the SANSurfer CLI tool to set the value for this parameter. For more information on how to set this parameter, see

http://download.qlogic.com/manual/32338/SN0054614-00B.pdf

Table 3-1 lists the heartbeat intervals and the node timeout values for a particular cluster.

Table 3-1		Cluster Reformation Time and Timeout Values

		Heartbeat	Cluster	Link Down
		Intervals	Reformation Time	Timeout Value

		1 second	38 seconds	40 seconds

		2 seconds	56 seconds	58 seconds

		5 seconds	140 seconds	142 seconds

		10 seconds	250 seconds	255 seconds


NOTE		The values in this table are approximate values. The actual time varies
		from system to system, depending on the system load.

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Chapter 3

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Contents Page Legal Notices Contents Disaster Scenarios and Their Handling Managing an MD Device Contents Contents Printing History Editions and ReleasesHP Printing Division Intended Audience Document OrganizationPage Related Page Disaster Tolerance Evaluating the Need for Disaster Tolerance Evaluating the Need for Disaster Tolerance Node 1 fails What is a Disaster Tolerant Architecture?High Availability Architecture Pkg B Client ConnectionsDisaster Tolerant Architecture Understanding Types of Disaster Tolerant Clusters Extended Distance ClustersFrom both storage devices Extended Distance Cluster Two Data Center Setup Benefits of Extended Distance Cluster Cluster Extension CLX Cluster Shows a CLX for a Linux Serviceguard cluster architecture CLX for Linux Serviceguard ClusterBenefits of CLX Differences Between Extended Distance Cluster and CLX Continental Cluster Data Cent er a Data Center B Los Angeles ClusterNew York Cluster Continental ClusterBenefits of Continentalclusters Comparison of Disaster Tolerant Solutions Continental Cluster With Cascading FailoverContinentalclusters Comparison of Disaster Tolerant Cluster SolutionsAttributes Extended Distance Cluster HP-UX onlyUnderstanding Types of Disaster Tolerant Clusters Understanding Types of Disaster Tolerant Clusters Understanding Types of Disaster Tolerant Clusters WAN EVA Disaster Tolerant Architecture Guidelines Protecting Nodes through Geographic DispersionProtecting Data through Replication Off-line Data ReplicationOn-line Data Replication Physical Data ReplicationAdvantages of physical replication in hardware are Disadvantages of physical replication in hardware areAdvantages of physical replication in software are Disadvantages of physical replication in software are Logical Data ReplicationDisadvantages of logical replication are Using Alternative Power Sources Ideal Data ReplicationData Center a Node 3 Power Circuit Alternative Power SourcesPower Circuit 1 node Creating Highly Available NetworkingDisaster Tolerant Local Area Networking Disaster Tolerant Wide Area NetworkingDisaster Tolerant Cluster Limitations Manage it in-house, or hire a service? Managing a Disaster Tolerant EnvironmentHow is the cluster maintained? Additional Disaster Tolerant Solutions Information Building an Extended Distance Types of Data Link for Storage Networking DwdmTwo Data Center and Quorum Service Location Architectures Two Data Center and Quorum Service Location Architectures Two Data Centers and Third Location with Dwdm and Quorum ServerTwo Data Center and Quorum Service Location Architectures Rules for Separate Network and Data Links Guidelines on Dwdm Links for Network and Data Guidelines on Dwdm Links for Network and Data Guidelines on Dwdm Links for Network and Data Chapter Configuring your Environment Understanding Software RAID Supported Operating Systems Installing the Extended Distance Cluster SoftwareInstalling XDC PrerequisitesVerifying the XDC Installation # rpm -Uvh xdc-A.01.00-0.rhel4.noarch.rpmInstalling the Extended Distance Cluster Software Configuring the Environment Configuring the Environment Configuring the Environment Configuring Multiple Paths to Storage Setting the Value of the Link Down Timeout ParameterCluster Reformation Time and Timeout Values Using Persistent Device Names Http//docs.hp.comCreating a Multiple Disk Device To Create and Assemble an MD Device# mdadm -A -R /dev/md0 /dev/hpdev/sde1 /dev/hpdev/sdf1 Chapter Linux #RAIDTAB= # MD RAID Commands To Create a Package Control Script Creating and Editing the Package Control ScriptsTo Edit the Datarep Variable To Configure the RAID Monitoring Service To Edit the Xdcconfig File parameterEditing the raid.conf File Cases to Consider when Setting Rpotarget RPO Target Definitions Chapter Multipledevices and Componentdevices Raidmonitorinterval Configuring your Environment for Software RAID Recovery Process What happens when this disaster occursDisaster Scenario Disaster Scenarios and Their Handling Disaster Scenarios and Their Handling# mdadm --remove /dev/md0 # mdadm -add /dev/md0 Dev/hpdev/mylink-sdf P1 uses a mirror md0 Run the following command to S2 is non-current by less # cmrunpkg packagename Execute the commands that With md0 consisting of only N1, for example Becomes accessible from N2 Center Disaster Scenarios and Their Handling Managing an MD Device Viewing the Status of the MD Device Cat /proc/mdstatStopping the MD Device Example A-1 Stopping the MD Device /dev/md0Starting the MD Device Example A-2 Starting the MD Device /dev/md0Removing and Adding an MD Mirror Component Disk # udevinfo -q symlink -n sdc1Adding a Mirror Component Device # mdadm --remove /dev/md0 /dev/hpdev/sdeIndex 104