Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
The following is the problem. Exact technical details might be slightly off, but basically... The problem is that part of iSCSI is a client saying, I want exclusive access to a certain block(s), and then no other client can access that block. If you have two nodes serving the same disk (primary/primary), and host A says sure you have reserved that block to one client, nothing is keeping host B from telling a different client it has the same block reserved. Most of the time it isn't a problem, as for most traffic each client will go after different sets of blocks. However, when allocating areas for new files, or growing files, there are some blocks that are common and bad things can happen if two clients think they have exclusive access to a block when they do not. The problem isn't so much with drbd, as it is with the iscsi target on host A must share the reservation information with host B. If there is a clustered iscsi target that is designed to do that, then all would be fine. > -----Original Message----- > From: drbd-user-bounces at lists.linbit.com [mailto:drbd-user- > bounces at lists.linbit.com] On Behalf Of Andreas Hofmeister > Sent: Tuesday, November 29, 2011 5:44 PM > To: drbd-user at lists.linbit.com > Subject: Re: [DRBD-user] Cluster filesystem question > > On 29.11.2011 21:17, Florian Haas wrote: > > On Mon, Nov 28, 2011 at 9:26 PM, Lars Ellenberg > > > 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/ > > Yes Florian, I did get that from Lars' response. > > I'm still want to understand what the actual problems are. And no, > google does not actually help in this regard. > > If I knew what questions to ask and where to look at, I can beg or bribe > the right people or even find the right code to patch. > > Ciao > Andi > _______________________________________________ > drbd-user mailing list > drbd-user at lists.linbit.com > http://lists.linbit.com/mailman/listinfo/drbd-user