[mythtv-users] Backend hardware advice - RAID suggestions - RAID TCO Comp Calc Spreadsheet

dave johnson DJ4904 at hotmail.com
Sun Jul 16 21:53:26 UTC 2006


I hate to have to put this so bluntly, but you are blatantly and absolutely wrong Brad.

As I stated in my previous email, I built this system over 6 months ago (last Nov to be exact, so 
hell, 8-mos).  Back then, 500GB drives (to take your example) were typically $320 (including 
tax/shipping/etc) and almost no rebates or anything like that available (I know, I kept "waiting" 
for them to drop).  Just for 5 drives, the cost would have been $1600.

Plus I would still require the RAID card (although I could have gotten an 8-port unit for about $180 
on ebay at the time).

So for the cost of your system, I would have spent around $1600.   I spent about $700.

So, by your calculations, even at $500/year for electricity, I can run my system for nearly 2 years 
before hitting the break-even point of just the cost of your "green" system, assuming your "green" 
system didn't use any electricity at all (!)  Not to mention that I am using this array for a lot 
more than just dumb storage... there is quite a bit of iSCSI traffic on the system so the extra 
spindles certainly help in that regard when the various computers are hitting the storage system 
(did I mention that the other systems use super-efficent laptop drives for boot (that i got for 
free... various 8 and 12GB models), and this array for their main program and media storage ?  oh, 
yeah, i did...)

Regardless,  I was not advocating "you must use many small disks as possible".  You seemed to have 
missed my main point, and that was "hardware raid, for any configuration more than 4 drives, is 
often a cheaper and more reliable setup than any software raid, take my 6mos old system for 
example...".  But you are right, in that to protect myself from the pundits, i should have added 
"for a given life span of around 4 years."

By contrast, your suggestion would be like someone building an 11x300GB-drive 3TB array today for 
$1000 in drives and you coming along in 6mos and blasting them because they "could build a 3TB array 
with just 5x750GB drives for the same cost since" (if they were $200ea by then).

But because your quick-to-jump conclusion piqued my interested of where the break-even point really 
was, I took 20min or so to put this sheet together (it took more more time to format it and put it 
up on the ftp server ;)


Here you go people : 
http://se30.com/users/grindingbassline/mythtv/RAID_TCO_Comp_Calc_v200607161445.zip

So... taking only drive power usage into consideration, it is actually a lot less power than you 
would expect.  Your scenario vs mine puts the break even point longer than 10 years. (assuming cost 
of power didn't increase - yet another assumption)


Have a good one !

-=dave

----- Original Message ----- 
From: "Brad Templeton" <brad+myth at templetons.com>
To: "Discussion about mythtv" <mythtv-users at mythtv.org>
Sent: Sunday, July 16, 2006 12:28 AM
Subject: Re: [mythtv-users] Backend hardware advice - RAID suggestions


On Fri, Jul 14, 2006 at 08:03:08PM -0700, dave johnson wrote:
> -11x200GB Seagate 7200.8 PATA HD ($43/ea - massive tripple-rebate coupon-hell at Fry's and a lot 
> of
> trust-worthy friends.  It took almost 3 months to get the rebates and one was denied because I
> probably filled one out wrong, so add $70 for "my mistake." ;)


How many watts are these drives?   Typically one sees 7 to 15w for such drives (slower
drives, 4500 or 5400 rpm are usually better - quieter, cooler, lower power, longer life).

With your two PSs how much power are you drawing for the whole system?  200 to 300
watts?  More?

In California (you said you went to Fry's) incremental power has gotten up to 19 cents/kwh.

That means 300 watts, running 24/7 costs $500 per year.   (In winter you save a bit
from the heat it gives you, but not a lot.  In summer you may be paying it back
in AC costs if you need AC.)

Even in places with cheaper 10 cent/kwh power, it's still almost $250 per year for
the power.

Forget about the damage to the environment, 11x200gb is just a bad way to do it
from an economic standpoint.    They have 500gb drives in Fry's for $175 I think.

So 5x500gb could do 2 TB RAID-5 if you really need RAID (you don't in my view, this is
not a system that needs 100% availability) for a bit more money ($875 for drives vs.
$540 for the 11x200gb without doing rebates, and without 2 power supplies.

But more to the point it would draw a lot less power, and make up the difference
in a year or so.   Quieter and smaller too.


> Never under estimate the power of the K.I.S.S. method :)

Never forget that power is becoming the most expensive component of any always-on PC,
especially in California and other places with expensive power.
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