Less known Solaris Features: Point-in-time copy with AVS - Part 1: Introduction

The basic idea of Point-in-Time copies is the idea to freeze the contents of a disk or a volume at a certain time, thus other processes can work on data of a certain point in time, while your application works on the original dataset and changes it. Why is this important? Let´s assume you want to make a backup. The problem is quite simple. When a backup takes longer than a few moments, the files backup first my represent an different state of the system than the files backup last. You backup is inconsistent, as you´ve done a backup of a moving target. Okay, you could simply freeze your application, copy it´s data to another disk (via cp or dd) and backup it from there or backup it directly and restart your application, but most of the time, this isn´t feasible. Let´s assume you have a multiterabyte database on your system. A simple copy can take quite a time, in this time your application doesn´t work (at least when you database has no backup mode). Okay, simple copy is to ineffective. We have to do it with other methods. This tutorial will show you the usage of a method integrated into Opensolaris and Solaris.