On 10 Květen 2012, 13:34, MauMau wrote: > The workload is TPC-C-like write-heavy one; DBT-2. They compared the > throughput of synchronous replication case against that of no replication > case. > > Today, they told me that they ran the test on two virtual machines on a > single physical machine. They also used pgpool-II in both cases. In > addition, they may have ran the applications and pgpool-II on the same > virtual machine as the database server. So they've run a test that is usually I/O bound on a single machine? If they've used the same I/O devices, I'm surprised the degradation was just 50%. If you have a system that can handle X IOPS, and you run two instances there, each will get ~X/2 IOPS. No magic can help here. Even if they used separate I/O devices, there are probably many things that are shared and can become a bottleneck in a virtualized environment. The setup is definitely very suspicious. > It sounded to me that the resource is so scarce that concurrency was low, > or > your assumption may be correct. I'll hear more about their environment > from > them. > > BTW it's pity that I cannot find any case study of performance of the > flagship feature of PostgreSQL 9.0/9.1, streaming replication... There were some nice talks about performance impact of sync rep, for example this one: http://www.2ndquadrant.com/static/2quad/media/pdfs/talks/SyncRepDurability.pdf There's also a video: http://www.youtube.com/watch?v=XL7j8hTd6R8 Tomas -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
