On Wed, 26 Jul 2000, Kurt Garloff wrote:
> On Mon, Jul 24, 2000 at 06:07:39PM +0200, Martin Peschke wrote:
> > I am just thinking about multiple paths in Fibre Channel environments
> > because of several FC adapters within a single host connected to the same
> > switched fabric.
>
> Be careful. As Linux does not know that the devices it sees multiple times
> (on each host adapter once) are actually the same, it will not ense data
> integrity. If you change the contents of a device (filesystem) on one
> adapter and read back from the other one, your buffer cache and your FS will
> look inconsistent.
I'm currently looking for ways to implement multipathing above the SCSI
stack or alternately within a HBA driver. In my opinion, such
solutions can only be workarounds. Multipathing
should be a midlayer facility, since it is related to different things of
the current midlayer, i.e. device scanning and error recovery. Currently I
see it from a Fibre Channel point of view. I do not know which
requirements will be raised by other future attachments, like
Firewire. But I think there is a need to discuss a stack that considers
different physical interfaces, their protocols and characteristics. The
current SCSI stack is designed for Parallel SCSI, even if someone wrote a
FC-4 backend.
Regards
Martin Peschke
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