Comparing ASM with ZFS

I’ll be presenting on the topic of ASM and ZFS at the forthcoming UKOUG UNIX SIG, on the 20th May. I’m really looking forward to the presentation as it will be first presentation I have given in the style of presentation zen. There will be no bullet points in the slides, indeed the slides themselves will be meaningless on their own, though they will be an appropriate accompaniment to the words i’ll be delivering.

I’m currently writing a word document that will be the take-away document for the presentation. So, I’d like to ask anyone popping by the blog, what kind of stuff they would like to see in a presentation on ASM and ZFS? Is there any topics you feel are not addressed all that often, that should go into a talk on this subject?

Below is the general outline of the presentation:

This presentation describes Oracle’s ASM and Sun’s ZFS file systems.  I will tell a little bit of their history and how they actually work.

I will also compare and contrast the file systems, giving an understanding of the benefits of each.

The idea for the presentation came about while I was watching one of the Chief designers of ZFS, Sun’s Bill Moore, give a talk on ZFS. I was of course impressed with the functionality of the file system, though I had heard quite a lot about it prior to this. What I found unexpectedly in the talk that really intrigued me, was that the language Bill was using and some of the concepts expounded on in the presentation would be familiar to a DBA audience.

I was also struck by some of the similarities between ASM and ZFS – they have some unique features in common – what I mean by that, is that there are some advantages a software RAID solution (which both of them are) have over hardware RAID.

I had been running ASM in production for around two years by this time (December 2007) and, I suspect like a lot of DBAs had in some ways treated ASM like a black box. I knew enough to install it and operate it, but knew very little about how it actually worked. In some ways I think Oracle are greatly responsible for this state of affairs, as the stunning lack of documentation available regarding ASM has only bred a lack of understanding.

To be fair, I think Oracle have partly addressed this issue with the 11g documentation set, which now includes a “Storage Administrator” guide. However, they really have only partly addressed this, in that this guide still does not really tell you very many details on how ASM actually works.There is though an ASM book: “Oracle Automatic Storage Management” by Nitin Vengurlekar, Murali Vallath, and Rich Long. This book covers the gap in the explanation of how ASM actually works.

The boundary of responsibility for storage administration has become increasingly blurred within organisations with the adoption of ASM. I think this means DBAs more than ever (though, you could argue it should always have been the case) need to understand storage concepts to be fully in a position to extract the maximum benefit from their storage.

Here I will present some of the ideas behind both ASM and ZFS giving some insight of the benefits of both storage solutions and some of the features they have in common as well as where they differ.

I hope that sounds interesting enough for a presentation, and if you have any tips on what to include I’ll consider every one received.


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