Okay, I just looked everywhere I could think of and didn't see anything
mentioned about support in Linux for a multibus failover configuration.
Basically, a disk would be accessible on several host adapters (SCSI
adapters, whatever) and can be accessed through whichever ones work. This
technique is used in (at least) VMS and NT to get more redundancy in
several high-end storage systems, Digital StorageWorks being the one I know
about. I'm interested in implementing this for Linux, but a few questions
first.
1. Is this done? Did I miss it somewhere? I'd hate to duplicate someone's
work.
2. I'm planning on adding some sort of new virtual block device on a new
major number that can be associated with a list of physical block devices
via (ioctl / proc filesystem) and forwards all access requests to the
currently preferred path. A failure would simply cause the next available
path to become preferred. This looks like it'll work okay. Anyone see
problems with this approach, or a better way?
3. Anyone have hardware that they can test this on? I don't, so if you do
and care about this, let me know. I'll e-mail you when I have something to
test.
I'd like to emphasize that this isn't gonna be done some time soon. I'm
just getting started with kernel hacking, and this just looked like
something cool to work on that actually has a point. If people are really
interested I'll try to get it done, but no guarantees.
Thanks,
Chris Smith <cd_smith@ou.edu>
PS: Please CC replies if convenient -- I'm subscribed to the list digest,
but I'll see direct mail a lot sooner.
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