>On Wed, 2008-09-10 at 18:37 -0400, Maurice Volaski wrote: >> >On Wed, 2008-09-10 at 15:00 -0400, Maurice Volaski wrote: >> >> >On Wed, 2008-09-10 at 14:36 -0400, Maurice Volaski wrote: >> >> >> A disadvantage, however, is that Sun StorageTek Availability Suite >> >> >> (AVS), the DRBD equivalent in OpenSolaris, is much less >>flexible than >> >> >> DRBD. For example, AVS is intended to replicate in one direction, >> >> >> from a primary to a secondary, whereas DRBD can switch on the fly. >> >> >> See >> >> >> http://www.opensolaris.org/jive/thread.jspa?threadID=68881&tstart=30 >> >> >> for details on this. >> >> > >> >> >I would be curious to see production environments "switching" direction >> >> >on the fly at that low level... Usually some top-level brain does that >> >> >in context of HA fail-over and so on. >> >> >> >> By switching on the fly, I mean if the primary services are taken >> >> down and then brought up on the secondary, the direction of >> >> synchronization gets reversed. That's not possible with AVS because... >> >> >> >> >well, AVS actually does reverse synchronization and does it very good. >> >> >> >> It's a one-time operation that "re-reverses" once it completes. >> > >> >When primary is repaired you want to have it on-line and retain the >> >changes made on the secondary. >> >> Not necessarily. Even when the primary is ready to go back into >> service, I may not want to revert to it for one reason or another. >> That means I am without a live mirror because AVS' realtime mirroring >> is only one direction, primary to secondary. > >This why I tried to state that this is not realistic environment for >non-shared storage HA deployments.
What's not realistic? DRBD's highly flexible ability to switch roles on the fly is a huge advantage over AVS. But this is not to say AVS is not realistic. It's just a limitation. >DRBD trying to emulate shared-storage >behavior at a wrong level where in fact usage of FC/iSCSI-connected >storage needs to be considered. This makes no sense to me. We're talking about mirroring the storage of two physical and independent systems. How did the concept of "shared storage" get in here? -- Maurice Volaski, [EMAIL PROTECTED] Computing Support, Rose F. Kennedy Center Albert Einstein College of Medicine of Yeshiva University _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
