Managing Other Stream Replication Settings; Minreps, Maxreps, And Defreps; Hpstartdelay; Managing Volumes - Dell DX6000 Administration Manual

6.4. Managing Other Stream Replication Settings

6.4.1. minreps, maxreps, and defreps

These options give an administrator the ability to control how many replicas of streams can be
created and maintained within a cluster. Since each individual stream can request a certain number
of replicas be created, these parameters allow the administrator to override those choices to
account for the characteristics of the cluster as a whole. The minreps option gives an administrator
the ability to globally set the minimum number of instances that any stream is allowed to have,
irrespective of its lifepoint specifications. This value is a floor and will override a lower value that
may be set by an application developer. If an application requests more instances than the minreps
value, the higher number requested by the application will be used. Similarly, the maxreps option
gives an administrator the ability to limit the requested number of replicas so that it cannot exceed
a certain value. For small clusters, maxreps could be set to the total number of nodes in the cluster,
thus preventing needless error messages when the cluster is unable to fully replicate streams
because there are too few nodes. The final option, defreps, allows the administrator to specify a
default number of replicas that is used only if an individual stream does not specify number of reps
in its lifepoints. As the names imply, maxreps should be at least as large as minreps and defreps
should fall between minreps and maxreps (inclusive).

6.4.2. hpStartDelay

The hpStartDelay option allows an administrator to control the delay before the health processor
begins checking the cluster for the required number of replicas for content stored on this node. This
delay window occurs once following the startup of a node and provides a grace period for other
nodes in the cluster to stabilize. This is useful in situations where an entire cluster must be shut
down and restarted.
The health processor helps maintain data integrity on the cluster by performing the following tasks:
• Verifies the correct number of replicas exist in the cluster and makes sure replicas are properly
distributed on subclusters.
• Enforces lifepoint policies (enforces replica counts and delete policies (terminal lifepoints
specifically) at different policy time intervals).
• Validates the object's MD5 on the disk and creates a new replica if it doesn't match. This can
happen over time because of disk errors.
• Periodically evaluates if an object is optimally stored in its current location.
• Defragments storage space on an as needed basis.

6.5. Managing Volumes

The vols option in the node or cluster configuration file specifies the volumes that DX Storage
uses. This specification includes the device names and optional flags for handling these volumes.
Only one vols parameter is allowed in a configuration file.
Warning
DX Storage erases any non-DX Storage data on all the volumes it uses. Dell
recommends you run DX Storage only on nodes that are free of non-DX Storage data.
Copyright © 2010 Caringo, Inc.
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Version 5.0
December 2010