Re: What's the best hardver for PostgreSQL 8.1?

David Lang wrote:
> raid 5 is bad for random writes as you state, but how does it do for
> sequential writes (for example data mining where you do a large import
> at one time, but seldom do other updates). I'm assuming a controller
> with a reasonable amount of battery-backed cache.

Random write performance (small block that only writes to 1 drive):
1 write requires N-1 reads + N writes --> 1/2N-1 %

Sequential write performance (write big enough block to use all N drives):
N-1 Write requires N writes --> N-1/N %

Assuming enough cache so all reads/writes are done in 1 transaction +
onboard processor calcs RAID parity fast enough to not cause an extra delay.