2009/9/3 Frederik Ramm <[email protected]> > Hi, > > That is supported by my own experiments. I loaded the 20090819 planet, > tarred the PostGIS partition so that I could quickly re-create the > scenario, and then applied the 20090819-20090820 daily diff with > osm2pgsql --slim in a number of different configurations: > > "plain" (nothing special, all on one hd)..... 270 minutes > "plain" with -C4000.......................... 262 minutes > with pg_xlog on other hd..................... 266 minutes > with all indexes on other hd................. 210 minutes > with the "slim mode" tables on other hd ..... 220 minutes > "crossed" (normal tables on disk 1, their > indexes on disk 2, slim tables on disk 2, > their indexes on disk 1)..................... 213 minutes > like "plain" but on a RAID-0 md device....... 191 minutes > like "plain" but on a RAID-1 md device....... 281 minutes > > I have not tried combinations of these; it is to be expected that the > -C4000 will speed up the RAID-0 value a little but that's as good as it > gets. Since the process is still disk bound, adding a third hd to the > RAID-0 array could again improve things. > > I haven't thoroughly tested read performance; I guess that the RAID-1 > should give slightly faster reads than RAID-0. > > I feel a bit like someone who has spent days to code something in > assembler only to find that writing it in C and having the compiler > produce machine code yields something more effective ;-) >
Thanks for those interesting tests. They are clearly interesting; the variations between them are not small. I am planning to invest on a nice machine to do some work, this is clearly giving me an idea of what I should get. Yes, it is too bad that SSD drives are still too expensive. I was considering for the new machine a RAID 10 (0+1) configuration, but I am wondering if a RAID 5 might not be more interesting in the end. Emilie Laffray
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