[Info-vax] Databases versus RMS

[Paul Sture]

On Wed, 18 Apr 2012 08:40:50 -0500, Bob Koehler wrote:

> In article <3ddb$4f8e9ccb$5ed43999$7815 at cache60.multikabel.net>, Dirk
> Munk <munk at home.nl> writes:
> 
>> Indeed it is not. Cobol for instance has the deferred write option.
> 
>    VMS was in large part, a product of Fortran times.  And VMS Fortran
>    is quite happy to buffer file data if you use the options in the OPEN
>    statement that tell it to do so.
> 
>    In practice, I only had to turn them off once.  All the other code I
>    worked with could simply reprocess the input data.  In fact I spend a
>    lot more time telling Fortran, C, ..., to increase the buffering.

I agree.  Most of the time I was trying to up buffer sizes for 
performance on large batch jobs.  I was mostly happy with the defaults 
for updates driven by interactive programs because I wanted those on disk 
reasonably swiftly.

Back in RT-11 days the easiest way to make sure stuff hit disk was to 
close the file :-)

>    But I still find it a PITA to have to sprinkle fsynch calls all
>    through my UNIX code when I want to decrease the buffering.

You might enjoy these discussions where Linus Torvalds got upset over  
Ext3 and Ext4 behaviour:

http://bit.ly/JcDKvX

"if you write your metadata earlier (say, every 5 sec) and the real data 
later (say, every 30 sec), you're actually more likely to see corrupt 
files than if you try to write them together... This is why I absolutely 
detest the idiotic ext3 writeback behavior. It literally does everything 
the wrong way around -- writing data later than the metadata that points 
to it. Whoever came up with that solution was a moron. No ifs, buts, or 
maybes about it."

And one comment I particularly like:

http://bit.ly/JcDGMK

--- start quote ---

Difficult to have an ACID-compliant db when you don't have an ACID-
compliant fs.


I read Ted T'so's response pointed to by Charlie, above. This bit of 
reasoning has me laughing:

> This sounds like a good thing, right? It is, except for badly written
> applications that don’t use fsync() or fdatasync(). Application writers
> had gotten lazy, because ext3 by default has a commit interval of 5
> seconds, and and uses a ...

Those damn application writers! The nerve of them to assume that the file 
system might actually store their data in reasonable time! What will they 
expect next? A database that stores data? An operating system that run 
the computer?
/sarcasm

--- end quote ---


-- 
Paul Sture