Specifications

Measuring Detailed Rate of Change
SteelEye DataKeeper can mirror daily, approximately:
T1 (1.5Mbps) - 14,000 MB/day (14 GB)
T3 (45Mbps) - 410,000 MB/day (410 GB)
Gigabit (1Gbps) - 5,000,000 MB/day (5 TB)
Measuring Detailed Rate of Change
The best way to collect Rate of Change data is to log disk write activity for some period of time (one
day, for instance) to determine what the peak disk write periods are.
To track disk write activity, create a cron job which will log the timestamp of the system followed by a
dump of /proc/diskstats. For example, to collect disk stats every two minutes, add the following link
to /etc/crontab:
*/2 * * * * root (date ; cat /proc/diskstats ) >> /path_
to/filename.txt
… wait for a day, week, etc … then disable the cron job and save the resulting data file in a safe
location.
Analyze Collected Detailed Rate of Change Data
The roc-calc-diskstats utility analyzes data collected in the previous step. This utility takes a
/proc/diskstats output file that contains output, logged over time, and calculates the rate of change of
the disks in the dataset.
roc-calc-diskstats
#!/usr/bin/perl
# Copyright (c) 2011, SIOS Technology, Corp.
# Author: Paul Clements
use strict;
sub msg {
printf STDERR @_;
}
sub dbg {
return if (! $ENV{'ROC_DEBUG'});
msg @_;
}
$0 =~ s@^.*/@@; # basename
sub usage {
msg "Usage: $0 <interval> <start-time> <iostat-data-file> [dev-list]\n";
SteelEye Protection Suite for Linux269