Category: Computers


What is High Availability? When do you need it? How do you create it and how do you measure it?

I am busy designing and building infrastructure for various “as a Service” service offerings

Web as a Service (IIS)
Data as a Service (SQL and Oracle)
Middleware as a Service

So I thought I would float a few questions

What is High Availability?
When do you need it?
How do you create it?
How do you measure it?

DISCUSS !!

[UPDATE]

Here is my two penneth,

Just in case anyone wondered what I actually do for a living, I build world class web hosting platforms. We are talking up to a Terabyte of content and 8-10 Million hits per day. So when a friend of a friend said he was having trouble with a site getting 190,000 hit per day, i did a detailed analysis and made some recomendations.

Then I hear they have been and done something completely different, and possibly daft.

Well I say good luck to him

Disk based backups and Earthquakes

About a month ago I was in an infrastructure meeting discussing backup strategy. The conversation was around disk based backups such as near store and Virtual tape libraries.
So I asked the question “do we know how these disk based backup system cope with earth quakes?”
As yesterdays data could be on the same disk that is being access today, a disk level corruption could be “interesting”
As the point in time I got laughed at, “Earthquakes, yeh right !”

Does not seem such a silly question now does it !

From BBC The biggest earthquake in the UK for nearly 25 years has shaken homes across large parts of the country.”

Nintendo DS WiFI

My son got a copy of the Nintendo DS transformers game for XMAS, and decided to try out the WiFi features over the weekend.
I had heard the some WiFi routers and access point do not work well as the DS wireless if not fully WiFi compliant. They aren???t kidding, more like not RFC compliant in many areas.
NO support for NON wep security
A TCP/IP stack that does not confirm it has taken the DHCP address it was offered and then does not respond to ping, instead it just uses it and says nothing, so the next new device connects to the network, gets the same address, and the DS gets kicked off,

It is a condition of my house insurance that I have a catalog of ALL my DVDs. I used to use a package called DVD profiler from invelos. After some digging I found my old licence key, which was upgraded for free to the latest version, they do a mobile version too, which means I can keep a copy on my PDA and know what DVDs I have next time I see any on offer (During that catalog I discovered I had two copies of memento and goonies). The software support bulk entry using a bar code scanner, which being a tech hoarder I have one stashed away which I acquired some time ago.

Now this is where the fun starts…..

Apparently bar code readers can be programmed, with pre amble and post amble characters, and various other options. This one seemed to be programmed to insert and ‘ESCAPE’ before the output and a ‘CR’ after, so in notepad it all looked fine, but the escape caused the data entry screen to ‘cancel’ DOH!
Time to RTFM for the scanner, to program the scanner, you scan special bar code from the programming manual.?? So print the manual, 10 Blank pages later, power cycle printer, 10 more blank pages, clean heads, 10 more blank pages, replace black ink, 10 more blank pages. DOH !!!!!!!
Of to the shops for a NEW printer, being a fully networked house hold it would be nice to have a network aware printer, and I hate trying to work out whats what from online reviews, so 5 shops and lots of box reading and helpless staff later, cheap Lexmark wireless printer from Sainsburys !

Print Manual, re program the reader, sorted.

Nah not that easy, some DVD barcodes have check digit, which is not sent by the reader, but it expected by the software, read the manual again, and enable check digit transmit,

Sorted, 350 Bar codes later. All done, 6 hours after I started !!!!!!!!!!!

Over the xmas break i thought i would review my data backup process, i have a few friends with kit at their house linked to mine via long range WiFi !, so File replication between server seemed like a good plan !
Got some big disks attached to each server using??USB 2, and setup replication, Sorted,
NAH, nothing is that easy,
NTFRS has got to be the most quirky thing ever to setup, my first word of advise, is go for a pint after you configure it, and BEFORE you put any data in the replicated folder. no in fact, that is No 2. No 1 has to be test you infrastructure HARD first.
My 1st snag was a delayed write error on my USB2 disk, which corrupted the USN data for the replicated folder, and completely screwed the whole replication process, after some soul searching, crying, fretting and LOTS of cursing. I reset the entire NTFRS config for that server.
Sorted I though, no such LUCK
another Delays write error, Closer inspection revealed i had been a cheap skate when i added USB2 to my aging server, it had a ???VIA??? chip, DOH!, DOH!, DOH!, DOH!, DOH!
Quick trip to a local computer retailer?? (not PCWorld), we have a local back street guy who is VERY good,
and i kissed good bye to the I/O issues. This is cool so i thought, all my data became “pre install” and everything seemed to be fine,
This is where the pint comes in, I “moved” (big mistake) my data from the pre_install folder to the replicate folder, and everything looked good, get up the next morning, NO DATA AROOGA AROOGA CURSE CURSE CURSE (BTW this was XMAS day, i have a record of upseting the wife, but tellting her i may have lost all the photos on XMAS would surely top it all)
after a week of searching volume shadows copies and offline data on all my PCs and friends servers, I had successfully recovered ALL our data, (can i have my testicles back now please)
so 1st things first MAKE Copy or three, and try again !
This time i did go for a pint or 3 before “COPYING” in my valuable data, and all i NOW Ok
all the data if almost fully synchronise across the servers, well 150 G of photos and other random data, will take a while to sync over wifi !
Some serious Lessons learnt
1. don???t fuck with your home IT on Xmas Eve
2. don???t rush NTFRS config
3. don???t MOVE data when you have the space to copy it

WiFi Survey

In a total geeky moment of boredom i have carried out a WiFi survey

Having used my tructy PDA and a copy of WiFiFoFum here are some of the results
Total discover access points 1005
Access point with NO Wep 227
Access points with BTHomeHub SSID 128
Access points with linksys SSID 39
Access points with belkin 93
Access points with livebox 27
Access points with sky 121
Access points with netgear 39
Access points with 2wire 22
Access points with BTopenzone 2
Access points with with hiden SSID 29
number of unique SSID 714

channel??number
1 313
2 11
3 12
4 10
5 9
6 209
7 18
8 7
9 26
10 16
11 351
12 6
13 17 (not sure how that works, not suppose to be available in the UK)

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Went Shopping at PCWorld over the weekend
Apart for the mental shock of stepping into PCWorld, I experienced something which just goes to highlight my thoughts about PCWorld Techies

The PCWorld till are windows 2000 based touch screen epos systems, so you woudl think, a PCWorld Techie would have no problem keeping them working,

however 2 of the 3 tills in the gloucester branch were offline due to Techincal problems

Go Figure

I am currently looking at Enterprise RSS technology. What a mine field !
No one knows what they want, let alone how to do it.
So I look at it like this.

1. Central location to discover internal and external RSS feeds
2. RSS feed consumption stats
3. Easy to use
4. Easy to configure
5. Flexible

Newsgator seem to provide all of the above. However with the small problem of a proprietary clients which then have to be deploy to 80,000-100,000 desktops (in my case), and you can guarantee that a large portion on the community (mainly the geeks) won???t like the client. So what you really need is a RSS Proxy server,?? that will consume, cache and aggregate RSS feeds and republish them as standard a RSS or ATOM feed, which can then be consumed by the users favourite RSS client (outlook 2007, IE7, Vista, Feedreader etc etc )
Only found one so far http://gregarius.net/ which is open source PHP, I have budget and can buy a solution but can???t find one.??

Are my requirements that bizarre ???

A corporate version of FEEDBURNER woudl be perfect