On 10/24/2013 4:12 PM, Lists wrote: > Going from HDD to SSD's gave us better than a 95% reduction in query > times for complex queries using PostgreSQL on otherwise identical > hardware. I wouldn't have believed it had I not seen it directly, for > myself. in some tests I ran, also using postgresql, a raid10 of 20 15000 rpm SAS2 hard drives performed about as fast as a raid0 of 4 SAS2 enterprise SSD's at a very write intensive highly concurrent OLTP style (many small updates) workload. both storage arrays were behind a HP SmartArray controller that had a 2GB write cache (with supercap/flash backup) when I exercised the SSDs for a week continuously such that their full capacity had been written several times over, they slowed down 2 or 3 to 1 from their original speed. at no point was the SSD array more than 50% full. -- john r pierce 37N 122W somewhere on the middle of the left coast