Re: Hard disk lit-up like Christmas tree ???

Thomas Cataldo wrote:
> On Thu, 2003-09-11 at 08:54, Arne Gehlhaar wrote:
> 
>>Kevin,
>>
>>you are not using file devices on a ReiserFS partition as database 
>>devices, are you? As you probably know, ReiserFS is a journaling 
>>filesystem, meaning every access to the fs is logged in a journal, which 
>>leads to a whole lot of extra i/o on your disk => not a very good idea 
>>for database devices (volumes). Use raw devices instead.
> 
> 
> Please have a look at this oracle 8i benchmark :
> 
> http://otn.oracle.com/oramag/webcolumns/2003/techarticles/scalzo_linux02.html
> 
> It clearly prooves you wrong as ext3 is the fastest performing fs on
> this test, and raw devices is clearly a bad choice under linux.

...but still better that ReiserFS.

But I don't think this article is very helpful. First of all it deals 
with Oracle, not SAPDB. So you know how well Oracle deals with raw 
devices on Linux but nothing more.

Secondly when it comes to data loss, I don't know how reliable a 
database volume sitting on top of a file system sitting on top of a 
logical volume manager sitting on top of a raid array sitting on top of 
a number of disks actually is. Of course a filesystem which uses read 
and write caches is faster than a raw device but caches are volatile 
which is what you don't want on a database device, at least I don't...

I'd like to know the performance of ext3 with its caches turned off!

Arne

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