Archive for June, 2010

Fundamentals of Storage Systems – RAID and Hard Disk Reliability, Under the Covers

In the last RAID article we covered the basics. This is a little deeper dive into the underlying mechanics of RAID. Exactly what it does, how it does it and what it doesn’t do that people assume it does. I sited David Patterson, Garth Gibson, and Randy Kats and their work at UC Berkley on RAID. They show something I’ve talked about before the “Pending I/O Crises”. Of course it isn’t pending anymore, its here. One of the concerns has to do with Amdah’s Law and speeding up execution with parallel operations. As processors and memory speed up hard disks are still an order of magnitude slower. More >

SQL Saturday #35 Notes and Observations

First of all, I want to congratulate all the volunteers that made this happen. It was a very well organized event and ran smoothly. I had a great time. It was nice meeting people that I couldn’t have met any other way.

 

As A Vendor… The Good:

Ryan Adams did a very good job keeping things coordinated up to the event. Making sure that everything we were entitled to we got. Always very responsive to emails and questions.

The day of I always had Ryan or one of the volunteers stop by between sessions and check that everything was good. I have always had a good experience with PASS events, but More >

What happens when Windows is the step-child? Adventures in Ruby on Rails.

Like many of you I’ve heard the developer community going on about Rails for quite a while now. It wasn’t until recently I had any reason to dip into that world. Over at Nitosphere the website is all run on Rails. We got a inexpensive web host and it was pretty easy to get it up and running. Like most shared web host, it is all linux/open source based. We have now grown to the point that hosting our own server would be cheap enough and give us complete control over the box. As a Microsoft ISV I thought it would be nice to have our new box be a Windows box. It would also be nice to hook in to More >

What I’ve Read and Recommend to Others – General Database and Theory by C.J. Date

Date on Database: Writings 2000-2006 This is a collection of writings by C.J. Date, one of the fathers of the relational model. It has a nice tribute to E.F. Codd, inventor of the relational model. If you are looking for tips and insights into relational databases on a higher level this is a solid read.  SQL and Relational Theory: How to Write Accurate SQL Code Another solid text from Date. This one helps you understand the theory so you can write effective real world code. It has lots of solid examples. It covers topics like granting More >

Sometimes, you have to fix it yourself

The Problem

SQL Server is a huge product with lots of moving parts. Bugs happen. Microsoft has a place to voice your issues or problems. They allow you to vote on the issue and then decide when or if it will get fixed. I’ve used Connect when I hit a bug and I have voted on items that were important to me. Recently I hit a bug in sp_createstats. I use this system stored procedure generate statistics in an automated process I’ve got that manages statistics. I added a new vendor database to the system and on the first run hit “Column ‘DAYSOPEN’ in table ‘dbo.TBL_OPPORTUNITY’ cannot be used in an More >

Quick Tip Of The Day

Over and over again we are told that the DMV’s only hold data since your last reboot. So, how do you know when your server was last rebooted? Well, every time your SQL Server service restarts tempdb is recreated every time. With a quick query to sys.databases we can get the creation date of tempdb! Armed with that little nugget you can then analyze what is in the DMV’s relevant to the last system restart.

SELECT

create_date AS last_restart_time

FROM

sys.databases

WHERE name = 'tempdb'

Three Turns On The Road

Huh? My story? Okay. It was never easy for me. I was born a poor black child. I remember the days, sittin’ on the porch with my family, singin’ and dancin’ down in Mississippi. – The Jerk

This meme was started by Paul Randal (Blog | Twitter) who asks the question "What three things or events brought you to where you are today?" I was tagged by David Taylor (Blog | Twitter). I wasn’t born in Mississippi but we sure were poor. I grew up I a small West Texas town of farmers and ranchers. I grew up between two households. I am a single child but have a large extended family and was a middle child More >

Out Of My Comfort Zone: Building a Web App

If you read Fundamentals of Storage Systems – Stripe Size, Block Size, and IO Patterns you know I built a little web tool to help you with sizing and estimating your RAID array’s performance. This is way out of my area of expertise. Luckily for me I like a challenge and had a guiding hand from some friends. I haven’t done any web programming since I wrote a photo album mod for Snitz! forum package in 2002, using classic ASP. I still get thank you emails from folks that have been running it for years. Needless to say my skills are a little rusty. My first instinct was to fire up Visual Studio More >

Fundamentals of Storage Systems – Stripe Size, Block Size, and IO Patterns

If you have been following this series we have covered system buses, hard disks, host bus adapters and RAID. Along the way we also covered how to capture your IO patterns and the SQLIO tool. Now we will pull it all together.We move up the stack even further to the actual layout of the RAID stripe and the file system. How the stripe and file system are laid out on your disks has a huge impact on performance. One of the things that has really gotten some traction over the last few years is sector alignment. This one thing, if not done, could cost you 30% to 40% of your IO potential. Jimmy May More >

Fundamentals of Storage Systems – RAID, An Introduction

In previous articles, we have covered the system bus, host bus adapters, and disk drives. Now we will move up the food chain at take a look at getting several disks to operate as one.

In 1988 David A. Patterson, Garth Gibson, and Randy H. Katz authored a seminal paper, A Case for Redundant Arrays of Inexpensive Disks (RAID). The main concept was to use off the shelf commodity hardware to provide better performance and reliability and a much lower price point than the current generation of storage. Even in 1988, we already knew that CPUs and memory were outpacing disk drives. To try to solve More >

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