POV-Ray : Newsgroups : povray.beta-test : That was close... Server Time
28 Jul 2024 14:31:55 EDT (-0400)
  That was close... (Message 1 to 7 of 7)  
From: clipka
Subject: That was close...
Date: 7 Jan 2009 00:50:00
Message: <web.49644176e3858249fe60fc2c0@news.povray.org>
Darn - one of my hard disks just suffered sudden death!

Looks like something killed the electronics; it still spins up and all, and the
system recognizes that it's there, but it doesn't even disclose its model name
to the BIOS anymore.

Fortunately it was "only" the brand-new Western Digital drive of my
just-as-brand-new Linux machine, and not the main HD in my Windows system... so
the only thing lost are a few shell scripts, a few hours' worth of rendering
time on some standard scenes, and a small deal of installation and
configuration work... plus a few minor updates to the radiosity tutorial I
posted not long ago. Nothing that couldn't be reconstructed in a few hours'
time.

If the same thing had happened to the - significantly older - main HD of my
Windows machine, it would have meant sayonara to something like a week of
brain-wrecking radiosity thinking and coding...

I just checked whether I was smart enough when setting up my project versioning
database: I was. If I should lose any single HD of my Windows system, I might
lose either recent work or the complete version history, but not both... phew!

Might also be a good occasion to dump the current versioning database to CD-ROM.


The nasty thing about it is that with the Linux system I lost my primary
performance testbed for the radiosity code, so unless I get a replacement soon
this might slow progress.


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From: nemesis
Subject: Re: That was close...
Date: 7 Jan 2009 13:40:01
Message: <web.4964f6d121b42647e44542980@news.povray.org>
"clipka" <nomail@nomail> wrote:
> Darn - one of my hard disks just suffered sudden death!

I felt a sudden death experience until reading the following paragraphs! XD


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From: stbenge
Subject: Re: That was close...
Date: 7 Jan 2009 17:59:18
Message: <496533c6@news.povray.org>
clipka wrote:
> If the same thing had happened to the - significantly older - main HD of my
> Windows machine, it would have meant sayonara to something like a week of
> brain-wrecking radiosity thinking and coding...

This reminds me... I mentioned in p.b.images that I sometimes get black 
splotches in certain scenes using radiosity. It is not caused by 
reflecting or refracting objects in the scene; I've known about those 
artifacts for some time.

This problem is caused by something else. I ran into it again last 
night. The radiosity count was at 300 when it happened. As it turns out 
the problem has to do with my setting for adc_bailout. I had it set to a 
value of 0.1. I changed it to 1/256 and the black splotches are gone! I 
found no mention in the docs about such behavior, but it makes sense in 
a way. I don't know why raising the count would make black splotches 
suddenly appear though, but since I have a fix I don't really care at 
this point. I thought I'd let you know about it, just in case it's not 
supposed to work that way.

Sam


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From: clipka
Subject: Re: That was close...
Date: 7 Jan 2009 20:30:00
Message: <web.4965569d21b42647e6fcd2f30@news.povray.org>
stbenge <^@hotmail.com> wrote:
> This problem is caused by something else. I ran into it again last
> night. The radiosity count was at 300 when it happened. As it turns out
> the problem has to do with my setting for adc_bailout. I had it set to a
> value of 0.1. I changed it to 1/256 and the black splotches are gone! I
> found no mention in the docs about such behavior, but it makes sense in
> a way.

Hum... why should it make sense to get black splotches if your adc bailout is
too high? ;)


> I don't know why raising the count would make black splotches
> suddenly appear though, but since I have a fix I don't really care at
> this point. I thought I'd let you know about it, just in case it's not
> supposed to work that way.

It is indeed not supposed to. But I expected something like this from the code -
I just didn't bother to try and come up with a test scene - instead I just fixed
that thing... ;)

It's quite a similar problem as with the max trace level: In both cases, if some
ray caused a sample to be taken, the relevant values (current trace level and
weight) were "inherited" by the sampling rays. If the origonal ray happened to
be reflected, these values would leave comparatively few trace iterations
(either due to the trace level, or due to the ADC bailout). But for the
surrounding samples the original rays might have come directly from the camera,
equipping the sampling rays with both a higher number of trace levels to go and
a heavier weight, so they might see a mirror or window where that other sample
just saw a pitch black square.


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From: Mike Hough
Subject: Re: That was close...
Date: 8 Jan 2009 19:45:09
Message: <49669e15$1@news.povray.org>
I have found that hard drives are not as reliable as they used to be. 
Several years ago I lost my main drive and hadn't made a backup for several 
months. It was the main reason I stopped doing graphics for several years. 
Since then I have always had several copies of my data and always have a 
RAID 1 setup. Hard drives are so big these days and relatively inexpensive 
there really is no reason not to. On paper the chance of losing both disks 
is 0.25%, although realistically it is probably a little higher. It has been 
a nice setup, since I have had drives fail over the years and have been able 
to just replace the drive and mirror without any major downtime or hassle. I 
make a point to keep any non-essentials like programs and the OS on a 
different disk since these are most likely to frag a disk(yes, I use 
Windows). I guess that sounds a little paranoid...

Mike


"clipka" <nomail@nomail> wrote in message 
news:web.49644176e3858249fe60fc2c0@news.povray.org...
> Darn - one of my hard disks just suffered sudden death!
>
> Looks like something killed the electronics; it still spins up and all, 
> and the
> system recognizes that it's there, but it doesn't even disclose its model 
> name
> to the BIOS anymore.
>
> Fortunately it was "only" the brand-new Western Digital drive of my
> just-as-brand-new Linux machine, and not the main HD in my Windows 
> system... so
> the only thing lost are a few shell scripts, a few hours' worth of 
> rendering
> time on some standard scenes, and a small deal of installation and
> configuration work... plus a few minor updates to the radiosity tutorial I
> posted not long ago. Nothing that couldn't be reconstructed in a few 
> hours'
> time.
>
> If the same thing had happened to the - significantly older - main HD of 
> my
> Windows machine, it would have meant sayonara to something like a week of
> brain-wrecking radiosity thinking and coding...
>
> I just checked whether I was smart enough when setting up my project 
> versioning
> database: I was. If I should lose any single HD of my Windows system, I 
> might
> lose either recent work or the complete version history, but not both... 
> phew!
>
> Might also be a good occasion to dump the current versioning database to 
> CD-ROM.
>
>
> The nasty thing about it is that with the Linux system I lost my primary
> performance testbed for the radiosity code, so unless I get a replacement 
> soon
> this might slow progress.
>
>
>


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From: clipka
Subject: Re: That was close...
Date: 10 Jan 2009 03:20:00
Message: <web.496859b321b42647f3c0a050@news.povray.org>
"Mike Hough" <nos### [at] nospamcom> wrote:
> I have found that hard drives are not as reliable as they used to be.
> Several years ago I lost my main drive and hadn't made a backup for several
> months. It was the main reason I stopped doing graphics for several years.
> Since then I have always had several copies of my data and always have a
> RAID 1 setup. Hard drives are so big these days and relatively inexpensive
> there really is no reason not to. On paper the chance of losing both disks
> is 0.25%, although realistically it is probably a little higher. It has been
> a nice setup, since I have had drives fail over the years and have been able
> to just replace the drive and mirror without any major downtime or hassle. I
> make a point to keep any non-essentials like programs and the OS on a
> different disk since these are most likely to frag a disk(yes, I use
> Windows). I guess that sounds a little paranoid...

It's actually the first hard drive I ever lose (well, the first one that is a
total loss, instead of just being mangled enough to start losing data and
wanting replacement), so you may be right. Maybe not too much of a surprise, as
the devices necessarily keep getting more and more delicate as the storage
density increases.

My wallet calls your approach paranoid indeed, but the security-aware computer
expert in me calls it wisdom... so far, it's just that my wallet has always had
the last say when it came to my personal stuff, righteously claiming that
"nothing has ever happened so far". So with that Linux machine mainboard having
five SATA channels, maybe it is time to go RAID.

My windows machine doesn't allow an easy transition to RAID, however. It does
have some BIOS support for RAID, but with only two SATA channels - and both of
them already in use (and the IDE channels just as well) - that might be a
daring quest in itself.


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From: Nicolas Alvarez
Subject: Re: That was close...
Date: 14 Jan 2009 17:43:39
Message: <496e6a9b@news.povray.org>
Mike Hough wrote:
> I have found that hard drives are not as reliable as they used to be.

Reliability doesn't sell. Capacity sells. Capacity involves putting bits
closer together, lowering reliability (they make them more reliable to
compensate for that but not enough).


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