FreeLists / haiku-development / [haiku-development] Re: writeback (was: Re: Re: Haiku self-hosting.)

[Luposian <luposian@xxxxxxx>]

On Apr 1, 2008, at 12:44 PM, Thom Holwerda wrote:

> On 1 apr 2008, at 21:08, Luposian wrote:
>
> > But press F12 (enter Kernel Debug mode) and type one short word... 
> > "reboot".  And hit [Enter].
> > The system reboots, and you go back into Haiku.  Look for your files. 
> >  ANY of them.  It can be 1 file or a dozen of them... they're NOT 
> > THERE!  Where'd they go?!?  They went bye-bye.  Why?  Because, 
> > although EVERYTHING said they were put on the disk, nice and safe and 
> > secure... THEY WERE NEVER REALLY THERE!
> Bad examples. Entering KDL and rebooting does not trigger a writeback, 
> and thus, stuff can be out of sync.
Oh, no... it's a PERFECT example.  What BeOS *DOES* do and Haiku SHOULD 
do, is writeback everything it needs to, WHEN it needs to.  And when it 
NEEDS to, is right after everything is ready for it to.  Such as when a 
file copy or creation or unpacking (or any disk write of one type of 
another) is performed.
I have waited 15 minutes after a file copy was performed and then did 
the F12+"reboot".  And my file(s) were gone, when I got back into 
Haiku.  Try running BeOS and even wait just 30 seconds after a file 
copy is performed and hit the reset button on your computer.  When BeOS 
comes back up, guess what... your file is right there!
So, which is better... an OS (Haiku) that never writes the files to the 
disk, unless you do an "expected" reboot/shutdown or an OS (BeOS) which 
does that immediately, so that no "sudden reboot" or power outage can 
catch you (or your files) off guard?
> This makes perfect sense, as entering KDL *should* halt everything.
Yes, I agree.  But the files are NEVER written to the disk, so it 
"halts" nothing, concerning file writes, because the file writes never 
took place, to begin with!
>  If you do a normal shutdown or reboot sequence, the first order of 
> business in that sequence is a writeback, syncing everything, making 
> sure the problems you describe do not occur.
And, in a perfect world, that would be fine.  In a world where there 
are no bad capacitors, no power outages, or people tripping over power 
cords or other "sudden accidents".  If you know where this type of 
world is, I'll gladly move there... seriously!  I think I heard it's 
somewhere around Dr. Seuss' Solla Salloo over the banks of the River 
Wahoo... :-)
> Most operating systems out there do it this way, since it's a lot 
> faster than doing things synchronously.
They don't include Windows XP or BeOS, I'm sure.  I plan to try my 
"sudden death" on my copy of Windows XP later tonight, to prove it.
> You might argue that this interval needs changing (I have no idea), 
> but that's a different issue.
I think I've already done that.  If Haiku writes files to the disk as 
quickly and as often as BeOS does, I believe I would be quite content.
> Yeah well yanking out power cables while the computer is powered on 
> and doing heavily file management is *never* a good idea - no matter 
> the operating system being used. You're asking the devs to fix 
> something that is essentially unfixable: power failures causing file 
> corruption.
I'm not talking about that kinda stuff happening WHILE a file is being 
copied or created or unpacked.  D'oh!  Of *COURSE* there would be file 
corruption.  The file is incomplete!  I'm talking about ehen a file is 
DONE being saved or copied or created or unpacked, etc.  My argument is 
that, that last step is NEVER done, in Haiku!  Not 30 seconds after the 
drive light goes out.  Not *15 minutes* after the drive light has been 
out.  N E V E R !!!
And, thus, as far as I can tell, all that drive light blinking and the 
time taken to supposedly copy a file (or whatever) is utterly 
MEANINGLESS!
The funny thing is... Haiku even shows that disk space is taken up, 
when you copy a file!  Yes!  Yet, when you do the afore mentioned 
F12+"reboot", the drive space ends up back where it was, before the 
file was ever copied... how is that possible, unless the file was never 
really there (taking up space), to begin with?  It looks to me like 
Haiku is LYING to me!
And, I'm sorry, but that is simply unacceptable to me.  110% 
unacceptable.
Luposian