Ross S. W. Walker wrote:
>
> If you were running a later kernel version of MD, it is conceivable
> that you could create a mirror with a remote storage drive over
> iscsi.
>
> It would be up to you though to figure out how to fail-over to it
> and to limit the bandwidth MD takes to that remote mirror and
> releasize that it will always be fully synchronous and so
> performance may not be the best over a WAN.
>
> You can also use a pair of vise grip plyers to do the job of an
> adjustable wrench, but it will probably strip the bolt in the
> process.
Unix has always been about combining tools that each do one job well. If
we already have a tool (iscsi) that exports remote block devices well,
following standards that would the actual storage to be on non-linux
devices, and another tool (md raid) that mirrors block devices, why not
combine them instead of inventing yet another special purpose tool? I
realize that drbd and nbd were developed before iscsi, but now that
there is a standard cross-platform network block device, why shouldn't
it be used? MD might need some new options to make it work as
efficiently in this scenario, but that seems like a more useful place to
add features - that is, there might be other situations where MD
mirroring to an external iscsi partition would be useful, or even
combining many iscsi exports into one raid volume.
--
Les Mikesell
lesmikesell at gmail.com