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Thursday October 13, 2005

ID Cards and the NIR Part 3 - Some thoughts on scale

Scale matters.

Now we get to muck about with some figures. Back of a envelope figures admittedly, but it does allow us to analyse this a little.

There are approximately 60 million people in the UK, and about 3/4 of these are entitled to an Identity Card. So let's say 45 million.

The Government wants to store 51 pieces of personal information on us. This, to me, looks like about 10k's worth of textual data, not counting how much it takes to store biometrics, images and so on. Biometric data seems to vary from hardly anything to 1000's of bytes so lets say another 10k for that. How big is a decent quality jpeg of yours truely? Well I reckon you could get away about 30-50k. Plus we need to add say 20% for encryption wrapping etc. So lets, for sake of easy calculation, say a given user profile starts at 100k per individual. Doesn't sound too bad.

So how much data storage are we talking about? 45,000,000 times 100k = 4,500,000,000k or 4,500,000megs or 4,500Gigabytes. Sounds a lot but it's only 4.5 terabytes and that wont cause much of a problem for a decent storage provider. That will probably fit on my PC in a couple of years time!

What about network bandwidth? This begs the question, how often are you going to use your ID Card? Lets start off working from where we are today. How often do you need to prove your identity to a high level of certainty? Open a bank account? Apply for a credit card? Maybe 3-4 times a year, probably less.

Ok, lets assume the whole card population uses their card 4 times a year. That is 180,000,000 card accesses per year, which is 493,150 per day, which is 20,547 per hour, which is 342 per minute, which is 5.7 per second. A fair old whack, but nothing that will scare the worlds greatest directory product (which, btw, has been benchmarked easily over 10,000 reads per second in a multi server environment, and even a single cpu server can support 1,000 reads per second.)

Yes, the network topography will be interesting, but that atleast is do-able.

How much traffic would be transferred for each access? Tricky, but at the worst case, assuming we transfer the whole 100k profile for each interaction and we need another 100k for protocol and security, that gives us 36 terabytes per year, 100 gigabytes per day, 4 gigabytes per hour, 1 gigabyte a minute and 17 megabytes per second. That's a nice collection of T1 pipes, no big deal.

So, we're home and dry then? Well, not quite. There are two other things we need to consider. The audit trail and the increase in usage of this system.

Lets take a look at the audit. Everytime you use the card the government wants to know. So your profile is going to get bigger. How big is an audit event? Could be anything from bytes to kbytes. If it is kbytes that storage is going to grow by perhaps a 100% per year, maybe even 300-400%. So we could guesstimate storage requirements at 18 terabytes per year, at the 4 uses per citizen per year rate. No worries, might need a couple of extra Sun boxes, and I haven't mentioned backup and fail over and redundancy obviously.

What about the increase in usage of the card over time? Well, lets say we start tieing the card to bank transactions, tube travel, bus and train tickets, congestion charging and toll booths. How often would you be using your card then? I reckon up to 10 times per day might be about on the money, perhaps even higher. What does that look like now?

Well, rather than 4 times a year the citizen is now using the card 3650 times a year. I won't bore you with more long maths, and assuming we're still auditing everything but based on the estimates above we now need...

Reads = 5200 per second
Network Bandwidth = 15 Gigabytes per second (You'd need 2,666 T3 lines working flat out)
1 Years Audit = 1642.5 Terabytes (assuming an audit event is 10kbytes)

What makes these figures scary? The combination of an audit and the scale. Can't help thinking that this audit is going to be a little on the expensive side.

Hmmm. Just as well we bought StorageTek. Time to buy some shares in Cisco too! ;-)

( Oct 13 2005, 12:31:46 PM BST / Oct 13 2005, 11:13:03 AM BST ) Permalink Comments [0]
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