[Linux-cluster] SCSI Reservations & Red Hat Cluster Suite

[Ryan O'Hara]

Tomasz Sucharzewski wrote:
> Hello,
> 
> Ryan O'Hara wrote:
>>> 4  - Limitations
> ...
>>> - Multipath devices are not currently supported.
> 
> What is the reason - it is strongly required to use at least two HBA in a SAN network, which is useless when using scsi reservation.
> 

It has to do with how dm-multipath handles ioctls. In brief, the SCSI 
registration/reservation commands use ioctls, and those need to be 
passed to all devices within a dm-multipath target. This is required for 
getting SCSI reservations to work, since all the I/O paths need to be 
registered correctly.

I believe that this is only a limitation for RHEL4. RHEL5 should have a 
fix that allows dm-multipath to properly pass ioctls to all devices.

-Ryan