Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On Mon, Nov 28, 2011 at 9:26 PM, Lars Ellenberg <lars.ellenberg at linbit.com> wrote: > "dual-primary" iscsi targets for multipath: does not work. > > iSCSI is a stateful protocol, there is more to it that than just reads and writes. > To run multipath (or multi-connections per session) > against *DISTINCT* targets [*] on separate nodes > > ** you'd need to have cluster aware iSCSI targets ** > > which coordinate with each other in some fashion. > > To my knowledge, this does not exist (not for linux, anyways). > > [*] which happen to live on top of data that, due to replication, > happens to be the same, most of the time, unless the replication link > was lost for whatever reason; in which case you absolutely want to make > sure that at least one box reboots hard before it even thinks about > completing or even submitting an other IO request... > > > Please do not try dual-primary DRBD exported as iSCSI target > on both nodes for multipathing or MS/C initiators. > > If you try anyways, it may appear to work for some time, > and then blow up in your face just when it is most inconvenient. > > > > If you want some single-primary drbd be exported on one node, > the other single-primary drbd exported on the other node, > that is certainly possible, and would at least distribute the > read load (writes have to hit both storage backends anways). > We can call that "active-active" as well, > just not within the same drbd. As this sort of issue currently pops up on IRC every other day, I've just posted this rant: http://fghaas.wordpress.com/2011/11/29/dual-primary-drbd-iscsi-and-multipath-dont-do-that/ ... in the hope that at least a few of those who are attempting to set this up are stopped in their tracks by googling first. Lars, if you object to this or would like some edits, please let me know or find me on IRC. Thanks. Cheers, Florian -- Need help with DRBD? http://www.hastexo.com/knowledge/drbd