Hi Lee, Thanks for detailed explanation!
Yes, you are correct. We allow users to modify the persistent target address, in case they mistyped it or say they later wish to reconfigure the IP address, without disruption to I/O. The patch we sent does ensure non disruptive I/O. Looks like though, there is a different standard practice to achieve this. Thanks for the recommendations on standard practices of using iSNS. Yes, similar to DNS addressing, makes a lot of sense on more thought. This seems to add a level of indirection, constant_name --> changing_ip_address. Looking into the iSNS asynchronous notification system. Thanks, Satyajit On Thu, May 31, 2018 at 2:59 PM, The Lee-Man <[email protected]> wrote: > On Wednesday, February 8, 2017 at 1:56:07 AM UTC-8, Satyajit Deshmukh > wrote: >> >> Hello, >> >> We have a setup, where we are using the iSCSI redirect functionality, >> where we connect to a highly available persistent address, and get >> redirected to a different address/portal. >> Our setup allows modifying the persistent IP address of the iSCSI >> targets, amongst active I/O to the iSCSI sessions to the redirected >> addresses/portals. >> The requirement is to ensure non-disruptive I/O when any portal crashes. >> (persistent address/portal is assumed to be still available) >> >> Consider a scenario where sessions are redirected to different >> addresses/portals and now the persistent portal address is modified on the >> target. >> >> Without this patch: >> When the redirected portal crashes, iscsid would tries to recover the >> session by reconnecting to the incorrect/stale in-memory 'failback_saddr' >> portal. >> Since, this IP is modified on the fly, iscsid tries reconnecting to a >> wrong portal. >> >> With the patch: >> Patch notifiies iscsid about the change in the persistent address of all >> the sessions via the iscsiadm utility. >> All in-memory session structures' failback addresses are updated with the >> new persistent address. >> >> We have unit-tested the patch in our setup and we can see sessions >> recovering amongst current portal failures. >> Usage: >> >> iscsiadm -m session -n updated_persistent_ip_address -v 192.168.5.5 >> >> Would be great if someone can review the attached patch. Any >> feedback/suggestions/questions greatly appreciated. >> >> Thanks, >> Satyajit >> > > > I haven't seen a reply from Chris yet (is there one I missed?), but I can > say I don't like this much. > > If I understand correctly, you're trying to handle the case where your > persisent target address/port changes. Is that correct? > > This is precisely the kind of thing that target directory services are > meant to deal with. Instead of having a hard-coded address, you look it up. > Also, iSNS (the target directory service) can even send asynchronous > notification of changes. > > Also, just as a piratical matter, changing the persistent address of Nodes > in use seems like changing a tire on a running car. > > Chris? > > -- > You received this message because you are subscribed to a topic in the > Google Groups "open-iscsi" group. > To unsubscribe from this topic, visit https://groups.google.com/d/ > topic/open-iscsi/SIKMWXXpQf0/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > [email protected]. > To post to this group, send email to [email protected]. > Visit this group at https://groups.google.com/group/open-iscsi. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "open-iscsi" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/open-iscsi. For more options, visit https://groups.google.com/d/optout.
