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Minimize failover time
microsoft.public.sqlserver.clustering microsoft.public.sqlserver.clustering
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Re: Minimize failover time -
09-10-2008
, 08:19 PM
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I explain better my reply. You said that "Reducing the failover time would result in lost transactions ...". Why? Why rendering faster the SQL recover would result in lost transactions? Thanks "Geoff N. Hiten" wrote: You cannot "save" a transaction that is not committed. By definition, it is incomplete and should be rolled back. Any completed transactions are rolled forward and are not lost. SQL 2005 and later make the database available after the roll-forward step as a means of reducing failover and startup time. -- Geoff N. Hiten Principal SQL Infrastructure Consultant Microsoft SQL Server MVP "Pasquale" <Pasquale (AT) discussions (DOT) microsoft.com> wrote in message news  ACE2259-9C29-4C64-A075-181CA47226C4 (AT) microsoft (DOT) com...Does exist a direct relation between failover time and transaction loss? Is it not possible to reduce the failover time and to save the transactions? Thanks "Geoff N. Hiten" wrote: Reducing the failover time would result in lost transactions. A failover event is much like a restart of the SQL Service. SQL Server must recover each user database by rolling forward committed transactions and rolling back uncommitted ones. There are some multi-tier architecture techniques that can isolate the front end web service databases from the actual back-end transactional ones, but those require significant application changes.to implement. -- Geoff N. Hiten Principal SQL Infrastructure Consultant Microsoft SQL Server MVP "Pasquale" <Pasquale (AT) discussions (DOT) microsoft.com> wrote in message news:42C8503C-7B6B-4FD6-843A-91F9F6648A94 (AT) microsoft (DOT) com... I have tried the failover by moving a resource group from one node to other one. The time registered refers to SQL Server resource recovering and not to entire group recovering. However, does exist a method to reduce the failover time (during a real event or not) to avoid loss transactions? Thanks "Tim Walsh" wrote: Keep in mind what has to happen when a cluster fails over or is moved to the other node. The cluster has to recognize the failure or the move request. The cluster then has to send SQL and the other resources shutdown signals and then wait for all the resources to respond. If the resources don't respond the cluster has to wait for the request to time-out before killing the resource. Once all the resources are off-line the cluster then has to send start signals to the resources on the other node and again wait for a response. The resources most likely have to start up in a particular order, so the start signals have to wait for each resource in the particular order to start and respond before the next resource can be sent a start signal. All of this signaling takes time, 15 to 20 seconds is actually pretty good response. I suspect you were testing the fail-over and this 15 to 20 seconds isn't based upon an actual failure where timeouts will most likely be encountered and a much slower response as a result. This is what clusters do, they don't guarentee that you won't have a service interruption, just that the service interruption will be shorter then if you had to manually respond. Highly reliable and highly available are not the same. "Pasquale" <Pasquale (AT) discussions (DOT) microsoft.com> wrote in message news:9C239FA3-ACC2-476B-AA1F-2EA208D056F9 (AT) microsoft (DOT) com... I have a two node cluster (active/active). When I try the failover with the cluster administrator tool I have seen that it occurs 15-20 seconds to recover the SQL Server resource. Is it possible to decrement the failover time for the SQL Server resource? How? Thanks |
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