Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On 12/01/2011 02:22 PM, Jake Smith wrote: > ----- Original Message ----- >> From: "Digimer" <linux at alteeve.com> >> To: drbd-user at lists.linbit.com >> Sent: Thursday, December 1, 2011 2:18:42 PM >> Subject: Re: [DRBD-user] Cluster filesystem question >> >> On 12/01/2011 02:13 PM, Lars Ellenberg wrote: >>> On Thu, Dec 01, 2011 at 01:58:15PM -0500, Kushnir, Michael >>> (NIH/NLM/LHC) [C] wrote: >>>> Hi Lars, >>>> >>>> I'm a bit confused by this discussion. Can you please clarify the >>>> difference? >>>> >>>> What I think you are saying is: >>>> >>>> OK: >>>> Dual-primary DRBD -> cluster aware something (OCFS, GFS, clvmd, >>>> etc...) -> exported via iSCSI on both nodes -> multipathed on the >>>> client >>> >>> No. >>> >>> OK: >>> Dual-primary DRBD (done right) -> cluster aware something (OCFS, >>> GFS, clvmd, etc...) >>> >>> NOT OK: >>> -> exported via iSCSI on both nodes -> multipathed on the client >>> >>> NOT OK: >>> anything non-cluster-aware using it "concurrently" on both nodes. >> >> What I've done in the past, and perhaps it isn't the wisest (Lars, >> Florian?), is to create a Dual-primary DRBD (with fencing!), then >> export >> it as-is to my nodes using a floating/virtual IP address managed by a >> simple cluster. >> >> Then on the clients (all of whom are in the same cluster), I mount >> the >> iSCSI target and set it up as a clustered LVM PV/VG/LVs. If you need >> a >> normal FS, then format one or more of the LVs using a cluster-aware >> FS. >> >> When the primary node (the one with the floating IP) fails, all the >> cluster has to do is move the IP down to the backup node and it's >> ready >> to go. I suppose you could just as easily do Primary/Secondary and >> include the promotion of the backup to primary as part of the >> failover, >> too. In my case, knowing I had fencing in place already, I went for >> the >> "simpler" cluster config of managing an IP only. >> > > I could be totally wrong but from what I read above you're not multipathing on your clients; just speeding up failover times; so (IMHO) you fit the "OK". But I'm sure one of the experts will weigh in. > :-) > > Jake This is true, I avoided multipath. I've heard too many difficulties with it's use, so I preferred simple/reliable over instant, particularly given iscsi's inherent robustness. In my case, the iSCSI-backed LVM LVs were used to host VMs. In one failure test, the fence failed and it was close to 30 seconds before I corrected the problem and recovery completed. Even in this long case, my VMs didn't fail (though they did block on disk i/o, of course). Again though, my experience only and I'm claiming no expertise. :) -- Digimer E-Mail: digimer at alteeve.com Freenode handle: digimer Papers and Projects: http://alteeve.com Node Assassin: http://nodeassassin.org "omg my singularity battery is dead again. stupid hawking radiation." - epitron