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From:Tyler Poland Date:October 23 2011 12:06pm
Subject:Re: 5.1.51 Database Replica Slows Down Suddenly, Lags For Days, and
Recovers Without Intervention
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Luis,

How large is your database?  Have you checked for an increase in write
activity on the master leading up to this? Are you running a backup against
the replica?

Thank you,
Tyler

Sent from my Droid Bionic
On Oct 23, 2011 5:40 AM, "Luis Motta Campos" <luismottacampos@stripped>
wrote:

> Fellow DBAs and MySQL Users
>
> [apologies for eventual duplicates - I've posted this to
> percona-discussion@stripped also]
>
> I've been hunting an issue with my database cluster for several months now
> without much success. Maybe I'm overlooking something here.
>
> I've been observing the database slowing down and lagging behind for
> thousands of seconds (sometimes over the course of several days) even
> without any query load besides replication itself.
>
> I am running Percona MySQL 5.1.51 (InnoDB plug-in version 1.12) on Dell
> R710 (6 x 3.5 inch 15K RPM disks in RAID10; 24GB RAM; 2x Quad-core Intel
> processors) running Debian Lenny. MySQL data, binary logs, relay logs,
> innodb log files are on separated partitions from each other, on a RAID
> system separated from the operating system disks.
>
> Default Storage Engine is InnoDB, and the usual InnoDB memory structures
> are stable and look healthy.
>
> I have about 500 (read) queries per second on average, and about 10% of
> this as writes on the master.
>
> I've been observing something that looks like between 6 and 10 pending
> reads per second uniformly on my cacti graphs.
>
> The issue is characterized by the server suddenly slowing down writes
> without any previous warning or change, and lagging behind for several
> thousand seconds (triggering all sorts of alerts on my monitoring system). I
> don't observe extra CPU activity, just a reduced disk access ratio (from
> about 5-6MB/s to 500KB/s) and replication lagging. I could correlate it
> neither InnoDB hashing activity, nor with long-running-queries, nor with
> background read/write thread activities.
>
> I don't have any clues of what is causing this behavior, and I'm unable to
> reproduce it under controlled conditions. I've observed the issue both on
> severs with and without workload (apart from the usual replication load). I
> am sure no changes were applied to the server or to the cluster.
>
> I'm looking forward for suggestions and theories on the issue - all ideas
> are welcome.
> Thank you for your time and attention,
> Kind regards,
> --
> Luis Motta Campos
> is a DBA, Foodie, and Photographer
>
>
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Thread
5.1.51 Database Replica Slows Down Suddenly, Lags For Days, and Recovers Without InterventionLuis Motta Campos23 Oct
  • Re: 5.1.51 Database Replica Slows Down Suddenly, Lags For Days, andRecovers Without InterventionTyler Poland23 Oct
    • Re: 5.1.51 Database Replica Slows Down Suddenly, Lags For Days, andRecovers Without InterventionClaudio Nanni23 Oct
      • RE: 5.1.51 Database Replica Slows Down Suddenly, Lags For Days, andRecovers Without InterventionHoward Hart23 Oct
        • Re: 5.1.51 Database Replica Slows Down Suddenly, Lags For Days, and Recovers Without InterventionLuis Motta Campos24 Oct
      • Re: 5.1.51 Database Replica Slows Down Suddenly, Lags For Days, and Recovers Without InterventionLuis Motta Campos24 Oct
    • Re: 5.1.51 Database Replica Slows Down Suddenly, Lags For Days, and Recovers Without InterventionLuis Motta Campos24 Oct