LARGE single-system Cyrus installs?

[Ian G Batten]

On 20 Nov 07, at 1332, Michael R. Gettes wrote:

> I am wondering about the use of fsync() on journal'd file systems
> as described below.  Shouldn't there be much less use of (or very
> little use) of fsync() on these types of systems?  Let the journal
> layer due its job and not force it within cyrus?  This would likely
> save a lot of system overhead.

fsync() forces the data to be queued to the disk.  A journaling  
filesystem won't usually make any difference, because no one wants to  
keep an intent log of every 1 byte write, or the 100 overwrites of  
the same block.  If you want every write() to go to disk,  
immediately, the filesystem layout doesn't really matter: it's just a  
matter of disk bandwidth.  Journalling filesystems are more usually  
concerned with metadata consistency, so that the filesystem isn't  
actively corrupt if the music stops at the wrong point in a directory  
create or something.

ian