manpages: LDMS description

util/man/LDMS_QuickStart

@@ -7,51 +7,53 @@ LDMS_QuickStart - man page for Quick Start of LDMS
 
 .SH INTRODUCTION
 LDMS is the Lightweight Distributed Metric Service. LDMS is a distributed data collection, transport, and storage tool that supports a wide variety of configuration options.
-The three major functional components are described below.
-The host daemon is the same base code in all cases; differ-
-entiation is based on configuration of plugins for sampling or
-storage and on configuring aggregation of data from other host daemons.
+There are three main functional components described below.
 .PP
 .I
 Samplers
-run one or more sampling plugins that periodically sample data of interest on monitored nodes. The sampling
-frequency is user defined and can be changed on the fly.
-Sampling plugins are written in C. Each plugin defines a
-collection of metrics called a metric set. Multiple plugins can
-be simultaneously active. By default each sampling plugin
-operates independently and asynchronously with respect to
-all others. Memory allocated for a particular metric set is
-overwritten by each successive sampling and no sample history
-is retained within a plugin or the host daemon.
+run one or more plugins that periodically sample data of interest. 
+Each plugin defines a group of metrics called a metric set.
+The sampling frequency is user defined and can be dynamically changed.
+A host can simultaneously run multiple plugins.
+Configuration flags determine whether the sampling plugins run synchronously or asynchonously
+(both on a host and across hosts). Memory allocated for a particular metric set is overwritten by each
+successive sampling. The host daemon does not retain sample history;
+plugins do not typically retain history, but can be written to do so.
 .PP
 .I
-Aggregators 
+Aggregators
 collect data in a pull fashion from samplers
-and/or other aggregators. As with the sampler, the frequency of
-collection is user defined and operates independently of other
+and/or other aggregators. The collection frequency
+is user defined and operates independently of other
 collection operations and sampling operations. Distinct metric
-sets can be collected and aggregated at different frequencies.
-Unlike the samplers, the aggregation schedule cannot be altered once set without restarting the aggregator. The number of
-hosts collected from by a single aggregator is referred to as the
-fan-in. The maximum fan-in varies by transport but is roughly
-9,000:1 for the socket transport in general and for the RDMA
-transport over Infiniband. It is > 15, 000 : 1 for RDMA over
-the Cray Gemini transport. Daisy chaining is not limited to two
-levels and multiple aggregators may aggregate from the same
-sampler or aggregator ldmsd. Fan-in at higher levels is limited
+sets can be collected at different frequencies. Once started, the aggregation schedule cannot
+be altered without restarting the aggregator. Fan-in refers to
+the number of hosts collected from by a single aggregator.
+Maximum fan-in varies by transport but is roughly
+9,000:1 for the socket transport and for the RDMA
+transport over Infiniband. It is > 15000:1 for RDMA over
+the Cray Gemini transport. Daisy chaining  is not limited to two levels;
+multiple aggregators may aggregate from the same sampler or aggregator ldmsd. 
+Fan-in at higher levels is limited
 by the aggregator host capabilities (CPU, memory, network
 bandwidth, and storage bandwidth).
 .PP
 .I
-Storage plugins
-write in a variety of formats. 
+Storage
+plugins write in a variety of formats. 
 Comma Separated Value (CSV) file storage of metric sets
-plugins are provided. The
-frequency of storage is dependent on the frequency with which
+plugins are provided. Storage occurs when a
 valid updated metric set data is collected by an aggregator that
 has been configured to write that data to storage. Collection of
 a metric set whose data has not been updated or is incomplete
-does not result in a write to storage in any format.
+does not result in a write to storage in any format. The store_derived_csv plugin
+can be configured to retain the immediately previous state history and thus store
+rate values.
+
+.PP
+The host daemon is the same base code in all cases; differentiation is based on configuration of plugins for sampling or
+storage and on configuring aggregation of data from other host daemons.
+
 
 .SH DESCRIPTION
 Quick Start instructions for LDMS (Lightweight Distributed Metric Service).