Archive for the ‘rant’ Category

How many IOPS can a single disk provide?

February 15th 2010

[edit]
I wish I could retract that comment about adding:- at the point the seek is done, you need to wait for the platter to spin into place, on average half a turn (the latency time). They do therefore happen in sequence! (If it was not for those pesky disks always spinning, I’d have been right!). Lesson learned: don’t let intuition lead you astray, don’t blog in haste, and realise that sometimes oft repeated advice is true. I am keeping the post up out of intellectual honesty, but will be blogging furiously to get it off the front page.
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I have just read an article on roughly how many IOPs you can expect from a single disk and encountered what I consider to be a frequently repeated mistake in the calculation.

Before I begin I want to point out that it is only an approximation anyway and caching in enterprise storage systems makes it perhaps a moot point anyway.

The article is here if you want to go and see it.
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Posted by tom under VMware & rant & storage | No Comments »

Arithmetic is a great bollocks detector

March 29th 2008

Go and read Pupils to get ‘new world’ trips from the beeb.

You may think “trips abroad for kids, great” , if you are more cynical you may think “heads choose the kids, not sure I like that”.

Let us do some arithmetic, 100 kids for 6 weeks each for £1.4M.

  • £1400000/100 = £14,000 per child
  • £14000/6 = £2′333 per week
  • Assuming a 40 hour working week, £58/hour

Of course its not that simple, the kids clearly don’t get all the money as if they had a 6 week job. I think a few marketeers in the UK, all the necessary admin by the British Council will do away with some of the money too, but I can’t imagine any way this is good value for the country or any organisation involved (I am not cynical enough to suggest that for the BC the point is to administer it.)

Hows about giving 1000 kids £1000 spend in a country of their choice, you could get them to bid for the money and report back with diaries and photos etc. All the £500’s the government paid into child trust funds for children with low-income parents could become a good jolly fund for them when they hit 18, or they could get driving lessons and a car – not a bad deal, particularly if their folks contribute anything else to the fund along the way. That or 18th birthday parties become 5 day benders in estates around Britain.

Posted by tom under Mathematics & rant | No Comments »