I don't think we are dealing with an IO bottleneck here because the slave server should quite faster with writings to the disc at least since we are using Raid 0 here. Or is there any way which could explain an IO bottleneck even though the slave is not running as many selects as the master is? In this case we are talking about one replicated database on a dedicated slave system.
Thanks, Hannes -----Ursprüngliche Nachricht----- Von: Mechain Marc [mailto:[EMAIL PROTECTED] Gesendet: Donnerstag, 10. Februar 2005 12:04 An: Hannes Rohde; Marc Slemko Cc: mysql@lists.mysql.com Betreff: RE: Slow Replication I think he is talking about the "innodb_flush_log_at_trx_commit" parameter. Try to put it at a value of 0. innodb_flush_log_at_trx_commit = 0 If you have an IO bottleneck, this may help. Marc. -----Message d'origine----- De : Hannes Rohde [mailto:[EMAIL PROTECTED] Envoyé : jeudi 10 février 2005 11:46 Ŕ : 'Marc Slemko' Cc : mysql@lists.mysql.com Objet : AW: Slow Replication I don't quite get what you mean with the second paragraph. Do you mean increasing the thread concurrency to 6 or something like that? I have already put it on 4 because we do have HT active on the cpu. On the other it is just a single processor P IV system. On other hand I think it wouldn't speed up the SQL thread on the slave a whole lot. It would be excellent if you could run two or more SQL threads on the slave you priories them somehow. Anyway I will try your last paragraph's suggestion. Thanks, Hannes -----Ursprüngliche Nachricht----- Von: Marc Slemko [mailto:[EMAIL PROTECTED] Gesendet: Donnerstag, 10. Februar 2005 11:24 An: Hannes Rohde Cc: mysql@lists.mysql.com Betreff: Re: Slow Replication On Wed, 9 Feb 2005 22:07:19 +0100, Hannes Rohde <[EMAIL PROTECTED]> wrote: > Hi all, > > We use MySQL as a database backend on a portal site. We have a two > database server setup (one master, one slave). The master is a PIV 3,2 GHz., > 2 GB Ram and a 80GB Raid-1 system. The slave is a PIV 3.2 GHz., 4 GB Ram and > a 80GB Raid-0 system. Both run on MySQL 4.1.9 and only use InnoDB. Even > though the slave is a bigger system and is quite fast with selects, it > always falls behind in replication (Seconds behind the server keeps growing > at high-load times). > Is there any way to speed up the replication a little more? I have already > tried a whole lot of things but have never been successful, yet :-( That can be problematic since innodb allows much higher concurrency than myisam, although you can still have this issue with myisam. What you have to realize is that due to how mysql replication works, every transaction needs to be serialized. The slave is only running a single statement at once. So if you have multiple CPUs on the server, or multiple disks that can't be saturated by a single concurrent operation ... then multiple simultaneous operations can get better performance on the server than you can get in replication to the client. If most of your stuff is innodb, then setting the innodb option to not sync to disk on every transaction may speed things up a lot ... if you don't care about your data. But, then again, I don't think mysql replication is actually fully transactional yet anyway. -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED] -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
