[dm-devel] multipath device question

[Stanislav Polášek <sp linworx cz>]

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Hi! Let me please start with apology for using the development list to
ask rather end-user question. I am looking for help with multipath
setup. I have a few servers connected to a ibm storage. Two servers have
two qlogic HBAs each. On the first server was created a multipath device
out of all 4 scsi devices/paths. On the second server it is possible to
assemble the same mp device and attach it without problems (there is the
gfs).

However, the third server I would like to connect to the storage has
just one HBA. It's only 1U format and I cannot add anything to it. And
moreover, the visible storage scsi device order there is different.

As I know the mdadm that I used to create the multipath device writes to
the superblock an information about the array, I would like to find out
how much the multipath implementation in the kernel depends on this
information. Would it be a problem to connect the third server to the
storage by assembling the multipath device out of just two scsi
devices/paths instead of four and in addition using scsi devices with
diferrent minor/major numbers?

As I do really doubt that, is there any way how to connect the third
server using the multipath setup?

Thank you very much for your help. I could get the answers by testing,
but these are production servers with terrabytes of data and I cannot
really stop them now for more then just a few minutes.

Stanislav Polasek

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Stanislav Polasek
RHCE #804005251615651 / RHCX
LinWorx s.r.o.
sp linworx cz / www.linworx.cz
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