Hi Alex,
We wanted an iSCSI SAN that has highly available data, hence the need
for 2 (or more storage devices) and a reliable storage network (omitted
from the diagram). Many of the articles I have read for iSCSI don't
address multipathing to the iSCSI devices, in our configuration iSCSI
Disk 1 presented as /dev/sdc and /dev/sdd on each server (and iSCSI Disk
2 presented as /dev/sde and /dev/sdf), but it wan't clear how to let the
servers know that the two iSCSI portals attached to the same target -
thus I used mdadm. Also, I wanted to raid the iSCSI disks to make sure
the data stays highly available - thus the second use of mdadm. Now we
had a single iSCSI raid array spread over 2 (or more) devices which
provides the iSCSI SAN. However, I wanted to make sure the servers did
not try to access the same data simultaneously, so I used GFS to ensure
correct use of the iSCSI SAN. If I understand correctly it seems like
the multipathing and raiding may be possible in Red Hat Cluster Suite
GFS without using iSCSI? Or to use iSCSI with some other software to
ensure proper locking happens for the iSCSI raid array? I am reading the
link you suggested to see what other people have done, but as always any
suggestions, etc are more than welcome.
Thanks, Mike
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