zfssa

Experimenting with the ZFSSA’s snapshot capability using the simulator part 2

In my last post I wrote down some notes about my experience while experimenting with the ZFSSA simulator. A simulator is a great way to get familiar with the user interface and general usability of a product. What I wanted to find out using the ZFSSA simulator was the answer to the question: “what happens to a clone of a database when I roll the master copy forward?”

In the first part of the series I explained how I created a clone of a database, named CLONE1. It is based on a backup of my NCDB database. On top of the backup I have created a snapshot as the basis for my clone. A clone in ZFS(SA) terminology is a writeable snapshot, and CLONE1 uses it. But what would happen to CLONE1 if I modified the source database, NCDB? And can I create a new clone-CLONE2-based on a new backup of the source without modifying the first clone? Let’s try this.

Changing the Source Database

Experimenting with the ZFSSA’s snapshot capability using the simulator

Recently I have been asked how the Copy-on-Write cloning works on the ZFS Storage Appliance. More specifically, the question was about the “master” copy: did it have to be static or could it be rolled forward? What better than a test to work out how it works. Unfortunately I don’t have an actual system available to me at home so I had to revert to the simulator, hoping that it represents the real appliance accurately.

Setup

First I downloaded the ZFS Storage Appliance Simulator from the Oracle website and created a nice, new, shiny storage system (albeit virtual). Furthermore I have an Oracle Linux 7 system with UEK3 that will attach to the ZFSSA using dNFS. The appliance has an IP address of 192.168.56.101 while the Linux system is accessible via 192.168.56.20. This is of course a virtual toy environment, a real life setup would be quite different using IPMP and multiple paths preferably over Infiniband.

Configuration