Sat Jul 17 17:17:38 PDT 2004
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> >> What is the size of your database, the size of your shared buffer > >> configuration, the work_mem settings and what is the read/write ratio of > >> your applications database access pattern? What is the average, min and > >> max row size of the replicated data? > > > > DB size is about 3GB. System RAM is 2GB. Shared buffers are at 16384 > > (130MB). Read/write ratio is probably over 99% read oriented. Row sizes > > are fairly average. No huge strings, and column counts are sane, 5-20 > > columns per table, about 60 tables. > > Under all those conditions you listed, I would shoot for the FSM. Adjust > max_fsm_pages to 250000 (yes, that's a quarter million), restart the > postmaster and do a "vacuum full analyze" on the whole database. Then > arrange for frequent vacuuming with pg_autovacuum or your own schedule. After turning up max_fsm_pages to 250,000, and max_fsm_relations to 12,500 (to maintain the 20:1 ratio in the default configuration), and did a vacuum full analyze, server load went up (cpu idle time down, context switches/sec up), but gradually reduced to the levels before I started having these troubles. In fact it worked so well, I had to check to make sure Slony-I was still running! It is, and the fetch statement durations are down to < 1ms times. So, that helped enormously. Would you mind explaining why? I can't seem to find a good explanation of the function the free space map serves, other than a message from Tom Lane regarding some enhancements to it, which gives some hints. Was it just Slony-I's high-turnover log tables which triggered this problem? Thanks, -Erik -- Erik G. Burrows - KG6HEA www.erikburrows.com PGP Key: http://www.erikburrows.com/files/erik.erikburrows.com.pgpkey
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