[Info-vax] Databases versus RMS

[Paul Sture]

On Sat, 21 Apr 2012 21:55:56 -0400, Arne Vajhøj wrote:

> On 4/21/2012 12:44 PM, Paul Sture wrote:
>> On Wed, 18 Apr 2012 08:40:50 -0500, Bob Koehler wrote:
>>>     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
> 
> I believe that you can disable the writeback caching at mount time.
> 

Indeed you can.  The trouble was that at the beginning of 2011 you had to 
know about this problem and put a more sensible value into your fstab 
yourself, for the default on ext4 at least wasn't the safest choice.

-- 
Paul Sture