Tuesday, 25 November 2008

Thin Provisioning or Good Practice, which is best? There's only one way to find out - Fight!

Marc Farley makes some interesting comparisons to storage purchasing decisions in a recent post. For the sake of disclosure, I do go to Costco and buy in bulk - no not 200lbs of chicken wings, but those things that can be divided and/or frozen (like salmon and coffee) - and more crucially things that don't become cheaper in price over time.

That is effectively Marc's argument; don't buy stuff you don't need yet because it will be cheaper in the future (not so with my salmon and coffee, I suggest). That's certainly true as we see a year on year reduction in storage per GB cost.

There are a number of reasons why people buy more than they need;

  1. New hardware deployment time is excessive due to datacentre restrictions and change control. In some sites this delay could be 3-6 months, so people work on the assumption that it's better to have more on the floor than be in a panic to deploy at the last minute.
  2. Business customers can't plan. It's a truism that everyone knows. Add on top the fact that chinese whispers inflate the original business requirement to two, three or four times more storage than actually needed.
  3. Vendors give discounts. Yes, shock! Vendors will sell you storage cheaper if you buy more. I know many places that buy complete arrays up front (even DMX-4 with 1920 drives!) to avoid the deploy time and get a better price.

There are many more reasons than this but you get the idea.

I've deliberately left off one issue - the inflexibility of some storage systems in their deployment method. Although this isn't directly a reason to buy more storage, it is certainly a reason why users hoard more storage on their servers. Monolithic arrays are way too slow at executing on configuration tasks and on dynamic rebalancing, requiring too much planning and thinking time to avoid bad layout and configuration issues.

So Marc, you should have stated that thin provisioning is only one aspect of reducing storage hoarding. Good practice is another. Flexible technology is an undoubted third.

Oh and 10 house points to the first non-UK person who can explain my post title!


Anil Gupta said...

"don't buy stuff you don't need yet because it will be cheaper in the future"

Is there a real-world study to support that? I have heard cost/GB argument for eternity. It doesn't fly because today you can buy from any vendor and tomorrow you can only buy from one vendor that you already chose during first transaction.

cost/GB assumes that you are free to buy from anyone today and tomorrow. No vendor is going to let you install any enclosure, any disk with their solution. A valid comparison will be comparison for buying bulk from one vendor today vs. buying incrementally from same vendor today and tomorrow.

Savings through negotiating when you are buying a solution today far exceeds bargaining power you have when you are already locked-in to a solution.

I met an end-user recently who purchased one petabyte of storage in one transaction. He already have few PB of storage bought incrementally. His argument was that he most probably paid for 500 - 600TB storage to buy 1PB in bulk using his previous incremental purchase experience with same vendor as baseline.

Chris M Evans said...


Firstly, I've always found that prices have come down. I leave it for others who purchase more frequently than I do to confirm this. Whilst I agree with you that the first & incremental purchase issue arises, this is easy to avoid with a dual vendor policy. I've advocated this many times; never let yourself be tied into one vendor or technology.

A dual vendor policy is easy to achieve, especially if you've the magnitude of purchasing power you mention in your 1PB example.

So for 1PB, did your end user deploy it fully from day 1? Did they calculate the cost of space, power, cooling to have that extra 500TB on the floor from the time they purchased it to the time they needed to use it?

If you're purchasing any generic storage technology, vendor lock-in doesn't have to be an issue. I know many organisations successfully managing to beat up the major vendors every time they purchase that next tranche of storage.

marcfarley said...


I haven't been able to figure out the title. I was working around "Fight the good fight", but couldn't come up with the angle I think you were asking for. Is it GOOD practices - as opposed to BEST practices?

Chris M Evans said...


Very puerile I'm afraid.