On 10/13/2010 06:43 AM, Fujii Masao wrote: > Unfortunately even enough standbys don't increase write-availability > unless you choose wait-forever. Because, after promoting one of > standbys to new master, you must keep all the transactions waiting > until at least one standby has connected to and caught up with new > master. Currently this wait time is not short.
Why is that? Don't the standbies just have to switch from one walsender to another? If there's any significant delay in switching, this either hurts availability or robustness, yes. > Hmm.. that increases the number of procedures which the users must > perform at the failover. I only consider fully automated failover. However, you seem to be worried about the initial setup of sync rep. > At least, the users seem to have to wait > until the standby has caught up with new master, increase quorum_commit > and then reload the configuration file. For switching from a single node to a sync replication setup with one or more standbies, that seems reasonable. There are way more components you need to setup or adjust in such a case (network, load balancer, alerting system and maybe even the application itself). There's really no other option, if you want the kind of robustness guarantee that sync rep with wait forever provides. OTOH, if you just replicate to whatever standby is there and don't care much if it isn't, the admin doesn't need to worry much about quorum_commit - it doesn't have much of an effect anyway. Regards Markus Wanner -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
