in all honesty is there a need really to replace the cluster. why not just add onto it?<br><br><div class="gmail_quote">On Mon, Jan 19, 2009 at 2:40 AM, Robert G. Brown <span dir="ltr"><<a href="mailto:rgb@phy.duke.edu">rgb@phy.duke.edu</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div class="Ih2E3d">On Sun, 18 Jan 2009, Greg Lindahl wrote:<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
On Fri, Jan 16, 2009 at 08:10:43PM -0500, Mark Hahn wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
The question was raised as "When should all these servers be upgraded or replaced again?"<br>
</blockquote>
<br>
3-5 years, IMO. if you replace hardware in <3 years, you're obviously<br>
burning money.<br>
</blockquote>
<br>
After factoring in rent and utilities, my replacement time is < 3<br>
years. So what's obvious to you doesn't seem very obvious to me!<br>
</blockquote>
<br></div>
Right. There are rules of thumb, but they are based on assumptions, and<br>
if the assumptions aren't applicable they will lead to non-optimal<br>
behavior. The right rule is "do the cost-benefit analysis and act<br>
according to what it tells you". Which will, in fact, often lead to 3-5<br>
year replacement cycle. But additional costs along the way alter the<br>
landscape, shifting to different replacement cycles.<br>
<br>
To do the computation correctly, you have to include all sorts of<br>
marginal costs and benefits. For example, sometimes there are nonlinear<br>
benefits to finishing work faster, which favors shorter cycles.<br>
Sometimes there are nonlinear costs (or higher than normal linear<br>
costs, which ALSO favors shorter cycles.<br>
<br>
On the other hand, if somebody else pays for the power, and you have no<br>
source of money to buy replacement nodes, you run nodes until they die.<br>
All the "usual" CBAs assume a constant flow of support moneys for new<br>
nodes, and that is not always the case.<br>
<br>
rgb<div class="Ih2E3d"><br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
-- greg<br>
<br>
<br>
<br>
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</blockquote>
<br></div><font color="#888888">
Robert G. Brown Phone(cell): 1-919-280-8443<br>
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</div></div></blockquote></div><br><br clear="all"><br>-- <br>Jonathan Aquilina<br>
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