lvmsar

lvmsar [ options ] [ interval [ count ] ]

interval
    The time in seconds between each reported sample. When specified without count, lvmsar reports statistics continuously until interrupted.

count
    The number of samples to be displayed. This parameter is typically used in conjunction with interval to collect a specific number of reports.

-f filename
    Reads statistics from a sar data file previously saved by sar or sadc. This allows for analysis of historical LVM activity collected over time.

-s hh:mm:ss
    Sets the starting time of the data for extraction. lvmsar will display records recorded from or after the specified time when reading from a data file.

-e hh:mm:ss
    Sets the ending time of the data for extraction. lvmsar will display records recorded up to or before the specified time when reading from a data file.

-o filename
    Saves the collected sar data to a file. This is typically used when lvmsar runs in data collection mode, often by implicitly calling sadc or sar -o internally.

lvmsar is a command-line utility used to collect and report statistics related to Logical Volume Manager (LVM) activity. It provides detailed insights into I/O operations on LVM logical volumes, including read/write requests, blocks transferred, and average queue lengths.

While lvmsar is often implemented as a wrapper script or an alias around the sar (System Activity Reporter) command using its LVM-specific options (e.g., sar -L), its purpose is to simplify access to LVM performance metrics.

System administrators utilize lvmsar to monitor the performance of their LVM-based storage infrastructure in real-time or analyze historical data. This helps in identifying potential bottlenecks, understanding I/O patterns, and making informed decisions regarding LVM configuration and optimization. It presents data in a human-readable format, making it easier to track LVM volume throughput and latency.

lvmsar is often a custom script or an alias wrapping the sar command with LVM-specific options rather than a standalone binary. Therefore, its exact availability, behavior, and supported options may vary between different Linux distributions or system configurations. It relies on the underlying sysstat package and sar's ability to collect LVM statistics. For historical data analysis, the sadc daemon (part of sysstat) must be running to regularly record system activity.

When run, lvmsar typically reports various metrics for each LVM logical volume. Key metrics often include:
rd_sec/s: Number of sectors read per second.
wr_sec/s: Number of sectors written per second.
avgrq-sz: The average size (in sectors) of the requests that were issued to the logical volume.
avgqu-sz: The average queue length of the requests that were issued to the logical volume.
%util: Percentage of CPU time during which I/O requests were issued to the logical volume (indicating its utilization rate).

The core functionality of reporting system activity, including disk I/O, has been present in Unix-like systems through sar since its inception (part of System V). As Logical Volume Management (LVM) became a standard feature for flexible storage administration on Linux, support for LVM-specific statistics was integrated into the sar utility (often via the -L option). The concept of a dedicated lvmsar command or script arose from the need to provide a more focused and convenient way for administrators to monitor LVM performance without sifting through the broader sar output. It reflects the evolution of system monitoring tools to cater to specialized storage technologies.

sar(1), lvm(8), iostat(1), vmstat(8), sadc(8)