Hi Piotr, resynchronization after a node or path failure is not on the iSCSI layer but above. In OHAC, HA ZFS is responsible to do the resilvering. Due to its internal structure, ZFS knows what blocks to update. Unfortunately one fix that is needed to make ZFS aware that an iSCSI path is back up again, is not in Open Solaris 2009.06 but only in a later build.
You're right that AVS supports async replication. But if you rely on async, aren't you better off with a full disaster recovery solution and not with a stretched cluster? Regards Hartmut On 06/15/09 09:46, Piotr Jasiukajtis wrote: > Hi, > > I have a question regarding current iSCSI solution and disaster recovery.. > How is solved data integrity after a node failure? > With AVS there is a bitmap so there is no need to synchronize a whole > disk/zpool. What about iSCSI based non shared storage? > AVS has one other advantage, it can work in async mode. > > On Mon, Jun 15, 2009 at 9:32 AM, Hartmut > Streppel<Hartmut.Streppel at sun.com> wrote: > >> Hi Nick, >> I was one of those who tried to push engineering to come up with a solution >> for a shared nothing cluster. And I am really glad that OHAC 2009.06 offers >> this capability with iSCSI targets and HA ZFS. >> >> Do we need AVS support? Good question. >> 1. For those Linux users who "grew up" with DRBD and Linux Heartbeat it is >> obviously an excellent fit to see the same architecture on Open Solaris. >> 2. On the other hand: >> - why introduce an additional - replication - layer, if you can achieve the >> same with less, i.e. with ZFS and iSCSI? >> - I do not see how the existing limitations of AVS in an OHAC environment >> can be solved easily: >> -- lack of persistence of AVS configuration data probably needs the >> introduction of CCR capabilities >> >> Regards >> Hartmut >> >> >> On 06/11/09 18:55, Nicholas Solter wrote: >> >>> Piotr Jasiukajtis wrote: >>> >>>> On Wed, Jun 10, 2009 at 7:20 PM, Nicholas Solter<Nicholas.Solter at >>>> sun.com> >>>> wrote: >>>> >>>>> Piotr Jasiukajtis wrote: >>>>> >>>>>> Hi, >>>>>> >>>>>> Colorado Main Requirements >>>>>> >>>>>> >>>>>> http://opensolaris.org/os/project/colorado/Requirements/ColoradoReqSpec.pdf >>>>>> says that Colorado in phase 2 will eliminate the requirement for >>>>>> shared storage by use Marcelo's ohac-avs project. Now in phase 1 we >>>>>> can use iSCSI to provide similar goal so will ohac-avs be integrated >>>>>> in phase 2? >>>>>> >>>>>> >>>>> Piotr, >>>>> >>>>> Good question ;-) >>>>> >>>>> Let me turn it around and ask you (and others on this list) whether you >>>>> would find AVS support useful? What other "hardware minimization" >>>>> features >>>>> would you like to see in OHAC? >>>>> >>>> I think ohac-avs will be useful to provide a non shared solution for >>>> VxFS and others in phase 3. >>>> What other minimization features? >>>> - iSCSI/FCoE instead of SAN >>>> - non shared replication in >3 node clusters >>>> - Geo AVS replication between clusters without shared storage >>>> - I think running Colorado nodes as PVM XEN domains would be >>>> interesting (at least for testing/developing) >>>> >>>> >>> Piotr, >>> >>> Thanks for the feedback! Anyone else who has opinions on this topic, >>> please email the list or feel free to email me privately. >>> >>> Thanks, >>> Nick >>> _______________________________________________ >>> ha-clusters-discuss mailing list >>> ha-clusters-discuss at opensolaris.org >>> http://mail.opensolaris.org/mailman/listinfo/ha-clusters-discuss >>> >> -- >> Sun Microsystems GmbH Hartmut Streppel >> Sonnenallee 1 Systems Practice >> D-85551 Kirchheim-Heimstetten Phone: +49 (0)89 46008 2563 Germany >> Mobile: +49 (0)172 8919711 >> http://www.sun.de FAX: +49 (0)89 46008 2572 >> mailto: hartmut.streppel at sun.com >> My BLOG: http://blogs.sun.com/Hartmut >> SAP Infos: http://wikis.sun.com/display/SAPonSun/SAP+on+Sun+Home >> Sitz der Gesellschaft >> Sun Microsystems GmbH, Sonnenallee 1, D-85551 Kirchheim-Heimstetten >> Amtsgericht M?nchen: HRB 161028 >> Gesch?ftsf?hrer: Thomas Schr?der, Wolfgang Engels, Wolf Frenkel >> Vorsitzender des Aufsichtsrates: Martin H?ring >> >> >> >> >> > > > > -- Sun Microsystems GmbH Hartmut Streppel Sonnenallee 1 Systems Practice D-85551 Kirchheim-Heimstetten Phone: +49 (0)89 46008 2563 Germany Mobile: +49 (0)172 8919711 http://www.sun.de FAX: +49 (0)89 46008 2572 mailto: hartmut.streppel at sun.com My BLOG: http://blogs.sun.com/Hartmut SAP Infos: http://wikis.sun.com/display/SAPonSun/SAP+on+Sun+Home Sitz der Gesellschaft Sun Microsystems GmbH, Sonnenallee 1, D-85551 Kirchheim-Heimstetten Amtsgericht M?nchen: HRB 161028 Gesch?ftsf?hrer: Thomas Schr?der, Wolfgang Engels, Wolf Frenkel Vorsitzender des Aufsichtsrates: Martin H?ring
