Alvaro Herrera <alvherre@xxxxxxxxxxxxxxxxx> writes: > Tom Lane escribió: >> Reorder to what, though? You still have the problem that we don't know >> much about the physical layout on-disk. > Well, to block numbers as a first step. fsync is a file-based operation, and we know exactly zip about the relative positions of different files on the disk. > However, this reminds me that sometimes we take the block-at-a-time > extension policy too seriously. Yeah, that's a huge performance penalty in some circumstances. > We had a customer that had a > performance problem because they were inserting lots of data to TOAST > tables, causing very frequent extensions. I kept wondering whether an > allocation policy that allocated several new blocks at a time could be > useful (but I didn't try it). This would also alleviate fragmentation, > thus helping the physical layout be more similar to logical block > numbers. That's not going to do anything towards reducing the actual I/O volume. Although I suppose it might be useful if it just cuts the number of seeks. regards, tom lane -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
