05.07.2011 21:29, Paul Reeves wrote: >> FW and HDD settings don't affect the page I/O stats. > > Actually, FW must affect the I/O stats
Sorry, but it doesn't not. Our I/O stats reports page writes performed by the engine (OS call). They could either reach the disk (FW=ON) or stay in the file system cache (FW=OFF), but the write has happened and it's reflected in the stats. >> These observations are true only for the statistics reported for >> stat_group = 0, as isql measures the database-wise statistics. > > Yes I know that the perf.h i/o stats are database wide. But in this case there > is no difference. The database is restored, isql attaches, does work, and > exits. There are no other concurrent connections and no other changes made to > the database. There can be no garbage collection under these circumstances. As > far as I understand it the perf i/o and the mon$ i/o should be measuring > almost exactly the same thing, except that the attachment level stats should > also include some extra I/O for the additional book-keeping. Wrong. I've already told you about the cache writer thread, which flushes dirty pages to disk in the background. > Ah, that is interesting. I don't think that is documented. I was under the > impression that stat_group 0 was cumulative for all connections since the > start of the server. Stats don't exist without active connections, as there are no resources kept inside the engine in the meantime. Dmitry ------------------------------------------------------------------------------ All of the data generated in your IT infrastructure is seriously valuable. Why? It contains a definitive record of application performance, security threats, fraudulent activity, and more. Splunk takes this data and makes sense of it. IT sense. And common sense. http://p.sf.net/sfu/splunk-d2d-c2 Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
