Re: XFS and RAID

[Steve Lord <lord@sgi.com>]

On Fri, 2002-05-24 at 14:57, Sidik Isani wrote:
> On Fri, May 24, 2002 at 10:23:22AM +0200, Seth Mos wrote:
> > [...]
> > Software raid5 will give you a much better performance. And if you make it 
> > with an external log onto the raid1(hardware) device it will perform a few 
> > hundred percent better then the hardware raid5 of the controller.
> 
>   I don't have a comparison of hardware vs. software raid, but I did
>   experiment with various software raid5+XFS configurations.  All tests
>   were on a single 400 MHz CPU with 6 13GB IDE (old, slowwww 7 MB/sec
>   drives).  This is our oldest RAID... no one would let me do "experiments"
>   on our newer >1TB configurations :-(  We have been running the 2.4.16
>   kernel with XFS.
> 
>   o 2.4.18+XFS-1.1 shows significant performance improvements,
>     especially in copying small files (30% faster) and removing
>     lots of files (300% faster.)  This is with an internal log.
> 
>   o Switching to an external log (as raid1 on partitions of two of the
>     same six disks that have the raid5) boosted small-file performance
>     by another 80% or so, even compared to an internal log with the
>     same 2.4.18 kernel.  So, even with XFS-1.1, an external log really
>     helped a lot here.


The real code to speed up raid5 internal logs is still pending here.
We found a couple of problems with it and part of it is getting
reworked. An existing filesystem will be able to use the new code.

Steve


-- 

Steve Lord                                      voice: +1-651-683-3511
Principal Engineer, Filesystem Software         email: lord@sgi.com