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...)

Oracle AWR Reports: When IOStats Lie


If you’ve been unfortunate enough to follow my dithering on Twitter recently you’ll know that I’ve been lurching between thinking that there is and isn’t a problem with Oracle’s tracking of I/O statistics in its AWR reports.

I’m now convinced there is a problem, but I can’t work out what causes it… so step 1 is to describe the problem here, after which step 2 will probably be to sit back and hope someone far (more...)

New Cookbook: Oracle Linux 6 Update 5 within an Oracle VM Template

Oracle-VMI’ve posted a new installation cookbook for using Oracle within a virtual machine running on Oracle VM. Surprisingly, I was unable to come up with a satisfactory method of accessing external storage that did not involve the use of Oracle ASMLib

Oracle Linux 6 Update 5 within an Oracle VM Template

Filed under: Blog, Cookbooks, Database, Flash, Linux, Storage Tagged: cookbooks, database, oracle, oracle vm

Understanding Flash: Unpredictable Write Performance


I’ve spent a lot of time in this blog series talking about the challenges involved in using flash, such as the way that pages have to be erased before they are written and the restriction that erase operations take place on a whole block. I also described the problem of erase operations being slow in comparison to reads and writes – and the resulting processes we have to put in place to manage that problem (i. (more...)

Oracle AWR Reports: When Averages Lie


I was recently contacted by a customer who runs a busy ERP system on their Oracle database. Their users have been screaming for some time about unpredictable performance, where application screens which would usually open in under a second suddenly take an age. ERP systems are legendary for this, of course, because as each screen loads the application tends to fire off a glut of queries to populate all the various fields, graphs and so (more...)

Understanding Flash: The Write Cliff


For the last couple of posts in this series I’ve been banging on about the importance of garbage collection (GC) in a flash system. I attempted to show you what happens if you don’t perform any GC at all (clue: you turn your flash device into a slow ROM), but clearly in the real world every flash array or SSD vendor has GC technology built into their flash translation layer. So why am I going (more...)

Postcard from Oracle OpenWorld 2014: The Oracle FS1 Flash Array


A couple of weeks ago I wrote a post about my trip to Oracle OpenWorld 2014 and the surprise announcement of the Oracle FS1 Flash Array. I posted it on the Violin Memory corporate website here:


Follow the link to find out whether I thought it was the most amazing product in the history of storage, or simply a rehashed Pillar Axiom hybrid array with some SSDs and a ton of marketing.


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...)