On Wed, May 21, 2008 at 7:12 PM, Michael O'Sullivan <michael.osullivan@xxxxxxxxxxxxxx> wrote: > 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. > I would not use multipath I/O with iSCSI unless you have specific reasons for doing so. iSCSI is only as highly-available as you network infrastructure allows it to be. If you have a full failover within the network then you don't need multipath. That simplifies configuration a lot. Provided your network core is fully redundant (both link and routing layers), you can connect 2 NICs on each server to separate switches and bond them (google for "channel bonding"). Once you have redundant network connection you can use the setup from the article I posted earlier. This will give you iSCSI endpoint failover. -Alex -- Linux-cluster mailing list Linux-cluster@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-cluster
