[CentOS] OT: Caching synchronous writes

On Thu, Apr 22, 2010 at 02:06:47PM -0700, nate wrote:
> Ray Van Dolson wrote:
> 
> > The "delayed allocation" features in ext4 (and xfs, reiser4) sound
> > interesting.  Might give a little performance boost for synchronous
> > write workloads....
> 
> Doesn't delayed allocation defeat the purpose of a synchronous write?

I don't know for sure.  From reading, it sounds like as far as data
integrity is concerned it would fall somewhere between complete
write-through synchronous writes and asynchronous writes.

> I think what you want is a proper storage array with mirrored write
> cache.

Which is what we have with ZFS + SSD-based ZIL for far less money than
a NetApp.

This[1] sounds interesting...

Ray

[1] http://lkml.org/lkml/2010/4/5/41