Aidan Van Dyk: > So, your SATA disk can do 43MB/s of sequential writes, but you're example > is doing: > 1) Sequential writes to WAL > 2) Random writes to your index > 3) Sequential writes to table heap > 4) Sequential writes to table' toast heap > 5) Any other OS-based FS overhead Ok, I see. Thanks a lot for the detailed answer! Especially writing to WAL may eat up 50% as I've learned now. So, 16MB/s x 2 would in fact be 32 MB/s, plus some extras... However, does that mean: If I have a raw sequential performance of 100%, I will get a binary write (like in my example) which is about 33% as a general rule of thumb? Just to mention: * The system has two hard disks, the first for WinXP, the second purely for the postgres data. * I was doing nothing else simultanously on the newly installed OS. * The consumed time (50s, see my test case) were needed to 99.9 % just by PGexecParam() function. * No network connect to the postgres server (everything local). * No complex sql command; just inserting 100x times using PGexecParam(), as a transaction. * The binary data was marked as such in PGexecParam (Format = 1). * What I meant by 43 MB/s "worst case": I downloaded some hd benchmarks which showed a performance of 43-70 MB/s. (Whereas repetitions of my postgres test did never vary, but *constantly* performed at 16MB/s). Hm. Nevertheless: If your explanation covers all what can be said about it then replacing the hard disk by a faster one should increase the performance here (I'll try to check that out). Thanks again! Felix -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
