Understanding Flash: Summary – NAND Flash Is A Royal Pain In The …


So this is it – the last article in my mini-series on understanding flash. This is the bit where I draw it all together in a neat conclusion that makes you think, “Yes! That was worth reading”. No pressure eh?

So let me start with the conclusion first: as a storage medium, NAND flash is a royal pain in the ass.


Why? Well, let’s look back at what we’ve learned in the previous 9 (more...)

The Great Hypervisor Bake-off: VMware ESX vs Oracle VM


This is a very simple post to show the results of some recent testing that Tom and I ran using Oracle SLOB on Violin to determine the impact of using virtualization. But before we get to that, I am duty bound to write a paragraph of text featuring lots of long sentences peppered with industry buzz words. Forgive me, it’s just the way I’m wired.

It is increasingly common these days to find database environments running (more...)

ASM Rebalance Too Slow? 3 Tips To Improve Rebalance Times


I’ve run into a few customers recently who have had problems with their ASM rebalance operations running too slowly. Surprisingly, there were some simple concepts being overlooked – and once these were understood, the rebalance times were dramatically improved. For that reason, I’m documenting the solutions here… I hope that somebody, somewhere benefits…

1. Don’t Overbalance

Every time you run an ALTER DISKGROUP <NAME> REBALANCE operation you initiate a large amount of I/O workload as (more...)

Implementing Linux native multipathing or DM-MPIO together with EMC PowerPath


Guest Post

I’m delighted to say that this is another guest post from my good friend Nate Fuzi, who performs the same role as me for Violin but is based in the US instead of EMEA. Because he is American, Nate thinks that scones are called “biscuits”, that chips are called “fries” and that there is nothing – *nothing* – that cannot be improved with the simple addition of bacon. Clearly, something is fundamentally wrong with him (more...)

Postcards from Storageland: Three Years At Violin


A few weeks ago, in what seems to be a truly modern phenomenon, I became aware that it was my third anniversary of joining Violin after I noticed a number of people congratulating me on LinkedIn. In many ways it feels like I’ve already been here for a lifetime, but it was only twelve months ago I was trying to think of a suitable flash-based pun for the title of an article just like this one. (more...)

Understanding Flash: Fabrication, Shrinkage and the Next Big Thing

Semiconductor Fabrication Plant (picture courtesy of SemiWiki.com)

Semiconductor Fabrication Plant (picture courtesy of SemiWiki.com)

Before I draw this series on Understanding Flash to a close, I wanted to briefly touch on the subject of manufacturing. Don’t worry, I’ve taken heed of the kind feedback I had after my floating gate transistor blog post (“Please stop talking about electrons!“) and will instead focus on the commercial aspects, because ultimately they affect the price you will be paying for your flash-based (more...)

Understanding Flash: Floating Gates and Wear


One of the important characteristics of flash memory is wear. We know from previous articles in this series that flash packages consist of dies, which contain planes, which contain blocks, which in turn contain pages. We also know that these pages contain individual cells which store the bits of data… but to understand what wear is we need to look a little bit closer at those cells, where we will find something called (more...)

SYNC 2014 !

Vanuit Proact organiseren wij het kennisplatform SYNC 2014 op 17 september in de Rotterdam Cruise Terminal. Alle hedendaagse IT-infrastructuurontwikkelingen in 1 dag: • Een interactief programma o.l.v. dagvoorzitter Lars Sørensen o.a. bekend van BNR • Een keynote van Marco Gianotten van Giarte, de Nederlandse “Gartner” op het gebied van Outsoucing/Managed Services • Huisman Equipment over de

Drill Down the I/O stack at UKOUG Tech13

It's just under a week to go before the doors open for the UKOUG Tech13 conference and the adjoining OakTable World UK 2013 sessions, so I thought I would write a very short blog post about what I will be doing there, where I'll be, and what I'm looking forward (more...)

How to detach storage device from running virtual machine in VirtualBox

In this post I want to show how to test what will happen with your cluster if you simply detach shared storage device from it. VirtualBox is great tool for that purpose because you can test such scenario without involving many people or causing any damage.

I am aware that (more...)

The effect of ASM redundancy/parity on read/write IOPS – SLOB test case! for Exadata and non-Exa environments

Last week I had a lengthy post at oracle-l that tackles Calibrate IO, Short Stroking, Stripe size, UEK kernel, and ASM redundancy effect on IOPS Exadata which you can read here
followed by interesting exchange of tweets with Kevin Closson here (see 06/21-22 tweets) which I was replying in between games at UnderwaterHockey US Nationals 2012 which we won the championship for the B division ;) I have my awesome photo with the medal here

This post will detail on the ASM redundancy/parity effect on IOPS… if… by changing the ASM redundancy (external, normal, and high) will it decrease the workload (more...)

NetApp’s ExaData Backup Play Reprise

I have received a fair number of responses to my previous post on this subject (some via comments and some via email). I thought the discussion worthwhile enough to punch it up a bit more here.


As I pointed out in the previous post, EMC can easily match NetApp's play to back up ExaData with the following:


As Geoff Rosser so correctly pointed out, this answer is incomplete. Yes, Data Domain is an awesome Oracle backup solution. Yes, it provides incredible deduplication rates for Oracle database environments. (Thanks, dynamox.) However, it is not the only viable solution from (more...)

Oracle datafile IO latency – Part 1

On my post about observing the Exadata V1 I had an interesting comment posted by Mark Seger (author of collectl and collectl utilities) about the correlation of activities across a system, the sample and snap time, and seeing the state of the subsystem before and after

The comment made me curious about the effect of snap intervals on the performance numbers of the datafiles and block devices.. especially on the latency numbers.. so I made a few test cases and created some scripts that would give me 5 seconds, 10 minutes, and 60 minutes output of (more...)