Cisco E2000 Router is solid when flashed with DD-WRT [Networking]

Posted on February 24, 2011 by OZ

Over a year ago I owned a Linksys WRT-54G V4 router configured as the main and a Netgear WNR8348 configured as a repeater bridge. Both running DD-WRT on wireless G. The solution was rock solid.

After several months, I decided to go the N route and got a Trendnet TEW-637AP and sold the Linksys. A very bad move. The Trendnet would not work as a repeater bridge (or client bridge), so I installed it as main router instead. The Netgear WNR8348, then configured as repeater bridge, started dropping packets and lost connectivity consistently.

Later I replaced the Netgear with an Asus RT-N12 and gave it away. I ended up in worse shape as the Asus lost connectivity every 15 minutes when copying large files; Netflix streaming was just impossible. I tried all kinds of configs (N, G, mixed, 20 Mhz, 40 Mhz, different power settings, you name them). It just did not work.

I was frustrated to the point of thinking about running physical cable but did not execute as it was going to be a very challenging task.

Last attempt to migrate to Wireless N:

I decided to give it a try to a pair of Cisco E2000 routers to replace my repeater bridges which got flashed with DD-WRT as soon as they arrived. I was really surprised with the positive results they gave me after transferring ISO files over wireless, to the point that they were maxing out my PC LAN port consistently. The only change I made was to lower the TX rate to 50 mW (default is 70 mW). The main Asus streaming wireless router is configured to serve N Only connection at channel 7 (2.4 Ghz) and Turbo Channel Width (40 Mhz).

Maxing out the LAN port

From now on, I will stick with Cisco or Linksys for my networking needs.

This is how my home network is configured currently:

Home Network

Migration to 2008 R2. Not as easy as Copy & Paste [Performance]

Posted on February 17, 2011 by OZ

We have gone through several migrations already, mixing and matching sources (SQL 2000, 2005, X86, X64, Enterprise to Standard, etc). We now got most of our databases running under SQL Server 2008 R2.

In every instance we have found performance issues related to HyperThreading, bad plans, missing registry key or outdated iSCSI drivers. We have reached a point where we are now ready to analyze and solve the challenges soon after the migration has been performed.

We recently migrated a core DB, from 2005 to 2008 R2, from X86 to X64 and from Enterprise Edition to Standard Edition. System was effective but the application was sporadically timing out. After digging through the logs, collecting info based on server side traces, and using Adam Machanic’s sp_whoisactive tool, we found the culprit. Eight services pulling data using 1 stored procedure was bringing the box to it’s knees. With updated stats, better hardware and more memory available, we never expected this to happen. But it did.

We added an index and narrowed the scope of a where clause inside the stored procedure. The procedure went from ~30 mins and ~100 million reads to 10 seconds and ~15,000 reads.

Small changes, huge differences. The key is to spot the issue, understand and work it around. Then schedule a production push and QA the process.

Reads out of hand

Things look very good now.

Your Smartphone. What if you lose it? [Security]

Posted on February 4, 2011 by OZ

Ever thought of that scenario? Not yet? Better start thinking about it now. If you work for a large corporation you might already be backed up by an enterprise level security system, but if you are not, then it’s time to get something in place to protect your information.

Work/Personal email, text messaging, sensitive documents, Facebook, Twitter, personal banking applications; you name them. An stranger can get access to them very easily (with banking application might be trickier, but at least they can try).

I use two products to protect my Android based phone in the case it gets lost or stolen.

Protector, an application that allows to setup a pin to access certain applications (fully configurable). This is very useful when you want to lend your smartphone to a friend for them to search but not allow them to open your email inbox for example.
Lookoput (available for Android, Windows Mobile and Blackberry). Protects your phone from viruses and backs up your information to their systems (calls, sms, etc). If you pay you get the premium options to locate, remote lock and remote wipe. These last 3 are the most important features for me.

Lookout

There are several other products out there you can try yourself.

Good Luck!

Allow me to sleep and focus on number crunching [#TSQL2sday]

Posted on January 11, 2011 by OZ

T-SQL Tuesday #014

It’s 2011 already and the first T-SQL Tuesday for the year has arrived.

This time the event is hosted by Jen McCown (Blog|Twitter), who just received an MVP nomination (congratulations Jen).

I have come up with a list that I want covered by my team this year, but my main goals are two: Allowing me to sleep properly and investing time on number crunching.

What does “allow me to sleep” mean?

Last year we started our migration project of all production database servers to High Availability solutions. We shall continue this year and finalize it. On the same token, homogenize our environment so every single business unit runs on SQL Server 2008 R2. We really spent time figuring out processes that cannot run in SQL Server 2005 (e.g. change data capture) and I need to make sure it does not happen anymore.

On the storage side, there are 2 projects running in parallel. One is to allow growth on a scalable solution which is already in place (stop concerning about hitting volume limits), and the second one to reduce data file footprint. The first project is trivial as we can hookup additional trays and expand volumes. The second one is more complex as we need to identify tables that hold historical data, partition them (if applicable), phase out old data and archive without impacting production applications.

On the monitoring side, we are creating a new project to see if we shall stick with Management Data Warehouse or get a 3^rd party tool to give us bird’s eye view of our systems at the DB level, define KPIs, and report based on them. We got proper HW and Service level monitoring in place already.

What does “focus on number crunching” mean?

This has 2 phases.

The first one is to work on a Master Metadata repository project and figure out relationships between different business entities. Then work with Business Owners and Data Analysts to figure out what should we report on, how far back should we do so, and what KPIs should be defined. This can allow us to continue building our Data Warehouse, extending ETLs, and allowing business unit A to correlate its data with Business Unit B.

This project is also tied with data file footprint reduction as we will be able to rollup information that shall be available on our DSS without the need of all the transactional data.

The second phase is analytics. This can be tied with data mining and statistics and will definitely involve some of the information we have stored in our cubes. We are still figuring this one out.

That is it for me on the technical side. On the managerial and personal? I would write about them on future blog posts.

What are your resolutions for 2011?

Solving the Garage Door Opener Safety Sensor Problem [DIY]

Posted on January 7, 2011 by OZ

What I expected to be a 15 minute fix became to be an almost 2 hour one. The main reason: the problem was not really related to the safety sensors, but a bad cable which I could not identify the first time. But it was worth changing them anyways as the original safety sensors were really worn out and not installed properly using any brackets at all. This was against code and was like it since I bought the house.

I proceeded to install the new safety sensors, and after ensuring that they were working properly. I installed the brackets 17 inches above the floor. Aligned the sensors and worked perfectly until I faced a new problem.

The garage door has thick horizontal wood bars which were wider than the distance provided by the brackets for installing the safety sensors. It was causing the door to open right when the first wood bar crossed the sensors. This was a big deal as it was not allowing the system to work properly. Seems the reason why the previous owner never installed the brackets in first place.

What I ended up doing was reversing the sensors so they face backwards instead. That was the only way to make them work. This garage door opener system was installed 7 years after the house was built, so my guess is that the wrong model was chosen.

There is always a workaround. The system is working properly now.