block network devices

[Bill Bogstad]

On Tue, Jun 23, 2009 at 10:35 PM, Dan Ritter<dsr-mzpnVDyJpH4k7aNtvndDlA at public.gmane.org> wrote:
>
> I've been looking at cluster filesystems over iSCSI and AoE, and
> on moderate hardware, performance appears to be execrable.
> Anyone around have experience with this sort of thing?
>
> For a simple example, I have:
>
> - a network that I can measure 93 MB/s across

> - a disk that I can measure 74 MB/s reading
> - a best-case ext3 over AoE of 41 MB/s

It seems to me that you are adding both network and filesystem
overhead here.  I just ran some quick 'dd's and I get similar
performance drops between direct reads of /dev/sd* and reads of large
files locally from an ext3 filesystem.  Interestingly,
I have another partition on the same disk formated as a  XFS
filesystem and local reads of a large file from that filesystem
gave me around 70 MB/s.  You might try AoE with XFS rather then ext3
and see what you get.

Bill Bogstad