What's the on disk cache size for each drive? The better HDD performance problem won't be sustained with large amounts of data and several different queries.
- - Ben Scherrey On Tue, Jul 17, 2018, 12:01 PM Neto pr <neto...@gmail.com> wrote: > Dear, > Some of you can help me understand this. > > This query plan is executed in the query below (query 9 of TPC-H > Benchmark, with scale 40, database with approximately 40 gb). > > The experiment consisted of running the query on a HDD (Raid zero). > Then the same query is executed on an SSD (Raid Zero). > > Why did the HDD (7200 rpm) perform better? > HDD - TIME 9 MINUTES > SSD - TIME 15 MINUTES > > As far as I know, the SSD has a reading that is 300 times faster than SSD. > > --- Execution Plans--- > ssd 40g > https://explain.depesz.com/s/rHkh > > hdd 40g > https://explain.depesz.com/s/l4sq > > Query ------------------------------------ > > select > nation, > o_year, > sum(amount) as sum_profit > from > ( > select > n_name as nation, > extract(year from o_orderdate) as o_year, > l_extendedprice * (1 - l_discount) - ps_supplycost * > l_quantity as amount > from > part, > supplier, > lineitem, > partsupp, > orders, > nation > where > s_suppkey = l_suppkey > and ps_suppkey = l_suppkey > and ps_partkey = l_partkey > and p_partkey = l_partkey > and o_orderkey = l_orderkey > and s_nationkey = n_nationkey > and p_name like '%orchid%' > ) as profit > group by > nation, > o_year > order by > nation, > o_year desc > >
