Re: Audacity and Gentoo

On Mon, 16 Jan 2006, Ian Rawlings stated:
> On 2006-01-16, Nix <nix-razor-pit@xxxxxxxxxxxxx> wrote:
>
>> Alas, if I put variable-speed fans into amaterasu I fear that the
>> machine will blink its fan-failure light
>
> I reckon a pair of wirecutters will fix that... Or some black
> insulation tape!

Oh, yes, but that light is *useful*; it tells me if the fans have
failed. (There's also a software flag that gets raised, and the
system sends me an email accordingly.)

>> Bore holes in the door. (Hell, I'm boring holes in the *ceiling* when
>> I move amaterasu into the loft, if the noise it makes up there is
>> tolerable. I've got to get power and networking and serial console
>> leads up there somehow.)
>
> I don't want to bore holes in the rack until I've figured out where I
> want the radio receiver to go on a more permanent basis. As for the
> utility of a radio receiver for timekeeping, it keeps it all nice and
> correct when I've got no net connection (for about 30 mins a year!)
> but the main reason it's there is because I like the idea, and I made

Sheer because-it-was-theredom :)

> it ages ago when I only had ISDN dialup. It cost me about £30 in
> parts and is made on a tiny bit of veroboard, not very complicated to
> make.
>
> http://www.buzzard.me.uk/jonathan/radioclock.html

Wow. That's a lot simpler than I thought. It may be simple enough even
for me. I might try and see if I can make one sometime this year.

> As for radio interference, with the amount of stuff in my rack and
> around the house, plus the hills around me that mean I can't pick up
> telly properly, or freeview, or DAB, and the fact that it's sat on top
> of the rack about 3 feet away from any of the foot-thick walls in an
> old stone-built house,

OK, you have worse radio reception than me :)

(no stone walls, and hills? this is Bedfordshire, we don't do hills.)

>> amaterasu has the OpenPROM bug that leads to it gaining about 15 minutes
>> a day, so precise millisecond-accurate syncs seem a little over the
>> top. I have to sync every ten minutes just to keep the time synched to
>> within a second.)
>
> NTP ought to cope with that, are you running NTP on your home network?

It does cope with that, but I haven't been running the daemon but just
kicking up ntpdate every so frequently. The daemon locks itself in
memory and things, and, well, I don't care about hyperaccurate clocks
*that* much.

> (BTW I'm a bit obsessive with accurate time, with four different
> sources of correct time that I can check against each other, two NTP
> sources and two non-computer sources)

.... while I have four computers synching against each other, and
two NTP sources on the net. I figure that if I drop off the net
my machines really won't care if their time is out of synch with it
because they're effectively out of causal contact.

(But I had to synch *closely* when I was using Coda. If the time is more
than a second out between replicated Coda servers, Coda throws a
wobbly.)

>> Well, *that* is crackers. Use 1U cases and set up cooling properly.
>> This is sort of the *point* of rackmountable cases, isn't it?
>
> To me, it's getting it all into one place with all the wiring safely
> out of the way,

Run the wires in conduit down the edges of the room, stick tower cases
in the corners of rooms between desks and bookshelves and wardrobes, and
abhor desktops. It seems to work; the only wire I normally see is a 20cm
length of network cable in my bedroom that I haven't bothered to wrap in
conduit yet. (Oh, and the places where the conduit stops and the cable
wriggles through holes in walls and that sort of thing.)

>> ... and this is what I use it for (perhaps I'm unusual in treating
>> it as a fun read).
>
> Yep, you are plainly bonkers.

Many have said so. :)

> I'm going to get mine going tonight and play R-Type for the first time
> in months.. Blast off and strike the evil Bydo empire!

I'll have to see if there's a Linux port of that :) I haven't played it
since, oh, the early 90s? The late 80s? Something like that.

>> Well, of course. Do it *right*. (Also, a lot of things really depend
>> on precise timings, undocumented instructions and so on, so the more
>> like the original hardware you can make it, the better. You might
>> slow some things down and make some others that never worked right
>> suddenly start to function.)
>
> Timing is also the reason behind another often-asked question, "why
> doesn't MAME make use of multiple processors", timing gets much harder
> to keep track of when you do that.

It's quite likely to slow it down, as well, and e.g. a CPU under
emulation would be very hard to parallelize.

(It's amazing how expensive distributed simulation can be. You have a
choice between slow-as-a-dog conservative synchronization algorithms or
faster-but-impossible-to-predict-runtime optimistic/predictive ones...)

>> Now that really *is* peculiar. Probably also trivially fixable (even if
>> distributed as a separate patch). I mean, what would be a better
>> emulation of the hardware than the hardware itself?
>
> I think we're talking old 3DFX chips here, MAME don't emulate anything
> that's still being seriously sold.

Ah, right. So it's not exactly a *problem*, then; I mean, how many
machines are there left with old 3Dfx's in them? They're S3-vintage,
aren't they? Even I retired my last S3 (a pre-Virge model) two years
ago.

>> Oh, that's what all the fibreglass in the loft is for. (Cold water tanks
>> catch fire all the time, donchaknow.)
>
> Really? I'll put a smoke alarm up there, about halfway down the
> inside of the tank...

:))

(and an ice alarm. How come nobody's thought of a way to do that? Watch
the temperature of the water, scream when it drops near 0C...)

>> Bah, if you want cool, go ARM.
>
> Price is an issue, ISTR the ARM boards were more expensive than the
> x86 clone boards, but there were some very small machines that looked
> quite nifty, Gumstix I think, but perhaps a little too small.

Yes, Gumstix rock. soekris are also very nice but more for network comms
and firewalling than for MAME, although I'm sure you could make a MAME
box out of one.

>> A term I don't know. How do you pipe heat? A solid copper tube?
>
> They're sort-of passive cooling devices, they transfer heat from one
> end of the metal flattened tube to the other using thermal convection
> of either a liquid or a gas, no moving parts like pumps, just the

.... no extra heat like Peltier arrays...

I guess it has a lower average temperature drop than a forced system
like a fridge, but that's not usually very important.

> convection. Usually you fix one end to the processor and the other to
> the case.

Interesting. I'll have a look around when I build my next machine and
see if I can find some.

>> Well, if you want to waste space, in a month or so you should be
>> able to stick Recant on it. Say what you like about database-backed
>> filesystems, space-efficient they aren't.
>
> Well, we all store stuff we don't need, how about automatically
> throwing half of it away?

The expirer does that, and it's not simple. However I did find a bug in
the design yesterday that would have accidentally expired files
corresponding to currently-visible inodes, and another bug today that
would have led to:

% echo 'foo' > a
% ln a b
% rm b
% echo 'bar' > b
% cat a
bar

> I had some tape drives that used to do
> that, very space efficient.

Mine were even more space efficient. They utilized an advanced form of
predictive coding, such that no matter what you put on the tapes, you
got `read error' off them again.

> I wonder if the lzip source code is still
> available now the web page has gone, you could integrate it into your
> filing system!

Hey, I could use lzo... but there's actually no point. One of the Recant
optimization threads resizes blocks according to read/write frequencies
(files that rarely get read or written, or that get read and written in
big chunks, will tend to have their blocks grow); when the blocks grow
above a certain size (8K, I think), PostgreSQL will take care of
compressing them for me. (Of course the block merger thread manages
compression ratios of 100% on duplicate blocks, discounting metadata,
but I can't expect that to always kick in as users have this strange
habit of not just writing copies of the same block over and over again.
They seem to actually want to store *data* and then *retrieve* it
again. But then despite this they go and use Oracle. This contradiction
is incomprehensible to me.)

> I was trying to make sense of the Lustre web pages, I'm not keen on
> reading too much into any pages that are linked from a page that
> states at the top that the information on them indicates what they
> want to do, and not necessarily what has been done!

i.e., it's a design document :) yep, you need one of those.

There is documentation in the download regarding what's *actually
there*. Note that like GFS it's designed with SANs and iSCSI and the
like in mind, and like GFS it doesn't *need* them and works perfectly
well on a reasonably speedy Ethernet network.

--
`Logic and human nature don't seem to mix very well,
unfortunately.' --- Velvet Wood
.

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