Invisible <voi### [at] devnull> wrote:
> >> Heh, I still remember looking at one of the stacks, and seeing that it
> >> had *seven* 4.2 GB drives in it. (Remember, in 1997, those suckers where
> >> EXPENSIVE.) I remember feeling slightly giddy trying to compute how much
> >> total storage space such a monster RAID setup... Ah, the memories.
> >
> > Indeed, I still recall that the Fortune 50 company I worked for a decade
> > ago had an EMC storage array with 750 GB of storage in it....
> >
> > My new *laptop* has a drive that big in it.  I've got about 4 TB of
> > storage here at home now.
>
> The fun thing is, apparently SSD has
>
> 1. Reached price levels where Normal Humans can potentially afford them.

Yep, I own two of them. A 60GB as a system drive for my desktop and a 120GB for
my laptop.
The performance improvement really is remarkable. And its not the burst speed
that is interesting but the random access transfer rates.

> 2. Reached capacities where you might actually buy this stuff.
>
> Interesting times ahead, eh?
>
> (Personally, I still can't figure out why SSD isn't several /million/
> times faster than a mechanical spinning disk, but hey...)

The read performance is actually mostly limited by the host interface (SATA3 is
up to 600MB/s nowadays) and the memory management of the SSD, write perfomance
largely depends on how fast the flash cells can be programmed.

Regards
Aydan

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Invisible <voi### [at] devnull> wrote:
> Actually, going back to my previous point: The amount of /moisture/
> emitted by a normal human is absurdly small. And yet, put enough of them
> in a room, and it can get astonishingly moist in there! o_O

I just had a look in Wikipedia:

1 human sweats about 400ml to 1l per day.


Now you just need the number of people and the size of the room to know how fast
it saturates.

Regards
Aydan

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On 23-1-2012 11:38, John VanSickle wrote:
> On 1/15/2012 6:05 AM, Orchid XP v8 wrote:
>>>> And also I'm assuming this is not cheap, so management do not want.
>>>
>>> Making something truly zero down-time is exceedingly expensive.
>>
>> Yeah, reducing down-time isn't usually too bad, but /zero/ down-time
>> requires going to absurd lengths.
>
> When I was stationed at Onizuka AFB, California (the Blue Cube, for
> those who live or work near the south end of the San Francisco Bay), we
> had two large SATCOM dishes, called Sun East and Sun West.
>
> One chronic problem was that getting downtime for preventive maintenance
> was as difficult as pulling gold teeth from a chicken. The user
> community (who was and always will be better connected than the
> maintenance community) were as stubborn as mules about allowing any
> downtime for any reason.
>
> "Hey, what if we took each dish down, once every six months, and do all
> of the preventive maintenance specified in the technical orders?"
>
> "No, no, we need those dishes up 24/7. Denied."
>
> You'll never guess what the result was.

Difficult.
my first guess would be that after 9-12 months the system failed for 
more than twice the time of the provocative maintenance.
but...
you said I couldn't guess. so that is not what happened.
ergo, the system was reliably working for 10 years until it was replaced 
by a better system with a small overlap in time.
...
No that can not be right, because if that was the case I guessed it, and 
I couldn't.
...
but, but, that would be true of every other guess...
...
...
Ah, I got it, I can not *guess* it, therefore I must *know* the answer: 
After 9-12 months the system failed for more than twice the time of the 
provocative maintenance.



-- 
tip: do not run in an unknown place when it is too dark to see the 
floor, unless you prefer to not use uppercase.

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On 23-1-2012 16:43, Invisible wrote:
>>>> So how much power do you think it takes to run 50,000 computers, plus
>>>> air conditioning for them, if each has (say) 150W power supply?
>>>
>>> As I say, the point is that most people will never see 50,000 computers
>>> in one place all at once.
>>
>> That isn't really necessary to be able to do the math....
>
> Sure, that's the great thing about math; it always works right, unlike
> intuition. ;-)
>
> But it's not a calculation most people would bother to make, because the
> power consumption of a PC is "negligible".
>
> In a similar vein, the heat output of a normal human in a large empty
> room is also negligible. But weirdly, if you put /a lot/ of humans in a
> room, no matter how big that room is, they manage to raise the
> temperature of the whole room. Unexpected, but true...

<boggle indeed>

I think the rule of thumb is that a person is about 100W. but any amount 
of power will heat any room even if only slighly unless:

a) the room is infinite in size
b) the room was warmer than a person to begin with (i.e. warmer than a 
person that is not cooled by outside temperatures)


-- 
tip: do not run in an unknown place when it is too dark to see the 
floor, unless you prefer to not use uppercase.

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On Mon, 23 Jan 2012 12:22:44 -0500, Aydan wrote:

> Invisible <voi### [at] devnull> wrote:
>> Actually, going back to my previous point: The amount of /moisture/
>> emitted by a normal human is absurdly small. And yet, put enough of
>> them in a room, and it can get astonishingly moist in there! o_O
> 
> I just had a look in Wikipedia:
> 1m³ of air at 20 can carry roughly 30ml of water (as vapour).
> 1 human sweats about 400ml to 1l per day.
> Since "normal" room air usualy has about 50% humidity that leaves about
> 15ml/m² for the sweat. That would mean 1 human can saturate 1 - 2.5 m³
> of air per hour.
> Now you just need the number of people and the size of the room to know
> how fast it saturates.

You'd also need to know the current relative humidity to know how 
saturated it is before you start adding people to the room.

0% humidity is quite rare - in fact, I don't know that it's possible on 
Earth other than in an artificial environment.  I live in a desert 
climate (though not in the desert), and while we do easily hit below 20% 
relative humidity, we don't hit 0.  (In fact, it's snowing right now)

Jim

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On 23/01/2012 05:22 PM, Aydan wrote:
> Invisible<voi### [at] devnull>  wrote:
>> Actually, going back to my previous point: The amount of /moisture/
>> emitted by a normal human is absurdly small. And yet, put enough of them
>> in a room, and it can get astonishingly moist in there! o_O
>
> I just had a look in Wikipedia:


20 what?

> 1 human sweats about 400ml to 1l per day.

You probably need to take breath moisture into account as well.

Even so, 1l/day is 41ml/hour - which is minute.



> Now you just need the number of people and the size of the room to know how fast
> it saturates.

I would suggest that sweat varies by temperature too. ;-)

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On 23/01/2012 08:35 PM, andrel wrote:

> I think the rule of thumb is that a person is about 100W.

That sounds like quite a lot...

...until you realise that 100W of heat is actually a very small amount. 
It takes 3.6 kW just to boil a small puddle of water inside an enclosed 
space (i.e., my kettle), and it takes several minutes to do that.

> but any amount
> of power will heat any room even if only slighly unless:
>
> a) the room is infinite in size
> b) the room was warmer than a person to begin with (i.e. warmer than a
> person that is not cooled by outside temperatures)

You forgot "unless the heat escapes the room faster than the heat source 
adds it". I've certainly seen houses so poorly insulated that short of a 
lava pit, the rooms are doomed to be at thermal equilibrium with the 
outside world.

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Invisible <voi### [at] devnull> wrote:
> On 23/01/2012 05:22 PM, Aydan wrote:
> > Invisible<voi### [at] devnull>  wrote:
> >> Actually, going back to my previous point: The amount of /moisture/
> >> emitted by a normal human is absurdly small. And yet, put enough of them
> >> in a room, and it can get astonishingly moist in there! o_O
> >
> > I just had a look in Wikipedia:

>
> 20 what?

centigrade.

> > 1 human sweats about 400ml to 1l per day.
>
> You probably need to take breath moisture into account as well.
>
> Even so, 1l/day is 41ml/hour - which is minute.


with a base humidity of 50%



> > Now you just need the number of people and the size of the room to know how fast
> > it saturates.
>
> I would suggest that sweat varies by temperature too. ;-)

and activity and ...

Regards
Aydan

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On 1/23/2012 3:25 PM, andrel wrote:
> On 23-1-2012 11:38, John VanSickle wrote:
>> On 1/15/2012 6:05 AM, Orchid XP v8 wrote:
>>>>> And also I'm assuming this is not cheap, so management do not want.
>>>>
>>>> Making something truly zero down-time is exceedingly expensive.
>>>
>>> Yeah, reducing down-time isn't usually too bad, but /zero/ down-time
>>> requires going to absurd lengths.
>>
>> When I was stationed at Onizuka AFB, California (the Blue Cube, for
>> those who live or work near the south end of the San Francisco Bay), we
>> had two large SATCOM dishes, called Sun East and Sun West.
>>
>> One chronic problem was that getting downtime for preventive maintenance
>> was as difficult as pulling gold teeth from a chicken. The user
>> community (who was and always will be better connected than the
>> maintenance community) were as stubborn as mules about allowing any
>> downtime for any reason.
>>
>> "Hey, what if we took each dish down, once every six months, and do all
>> of the preventive maintenance specified in the technical orders?"
>>
>> "No, no, we need those dishes up 24/7. Denied."
>>
>> You'll never guess what the result was.
>
> Difficult.
> my first guess would be that after 9-12 months the system failed for
> more than twice the time of the provocative maintenance.
> but...
> you said I couldn't guess. so that is not what happened.
> ergo, the system was reliably working for 10 years until it was replaced
> by a better system with a small overlap in time.
> ...
> No that can not be right, because if that was the case I guessed it, and
> I couldn't.
> ...
> but, but, that would be true of every other guess...
> ...
> ...
> Ah, I got it, I can not *guess* it, therefore I must *know* the answer:
> After 9-12 months the system failed for more than twice the time of the
> provocative maintenance.

While I was stationed there the systems were down around 5% to 10% of 
the time.

Regards,
John

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On 1/23/2012 5:53 PM, Jim Henderson wrote:
> On Mon, 23 Jan 2012 12:22:44 -0500, Aydan wrote:
>
>> Invisible<voi### [at] devnull>  wrote:
>>> Actually, going back to my previous point: The amount of /moisture/
>>> emitted by a normal human is absurdly small. And yet, put enough of
>>> them in a room, and it can get astonishingly moist in there! o_O
>>
>> I just had a look in Wikipedia:
>> 1m³ of air at 20 can carry roughly 30ml of water (as vapour).
>> 1 human sweats about 400ml to 1l per day.
>> Since "normal" room air usualy has about 50% humidity that leaves about
>> 15ml/m² for the sweat. That would mean 1 human can saturate 1 - 2.5 m³
>> of air per hour.
>> Now you just need the number of people and the size of the room to know
>> how fast it saturates.
>
> You'd also need to know the current relative humidity to know how
> saturated it is before you start adding people to the room.
>
> 0% humidity is quite rare - in fact, I don't know that it's possible on
> Earth other than in an artificial environment.  I live in a desert
> climate (though not in the desert), and while we do easily hit below 20%
> relative humidity, we don't hit 0.  (In fact, it's snowing right now)
>
> Jim
Cave system near here is.. damn close. Was going to be used as a bomb 
shelter, by the government, but, frankly, they would have had to store 
20 times the water they still have down there to survive it. You can 
definitely tell there is next to no water in the air while there.

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