On Dec 12, 2012, at 5:03 AM, Craig Ringer <cr...@2ndquadrant.com> wrote:
> On 12/12/2012 06:44 AM, Evgeny Shishkin wrote: >> >> On Dec 12, 2012, at 2:41 AM, Niels Kristian Schjødt >> <nielskrist...@autouncle.com> wrote: >> >>> Are you using a hardware based raid controller with them? >>> >> Yes, of course. Hardware raid with cache and bbu is a must. You can't get >> fast fsync without it. > > Most SSDs should offer fairly fast fsync without a hardware RAID controller, > as they do write-back caching. The trick is to find ones that do write-back > caching safely, so you don't get severe data corruption on power-loss. > Actually most of low-end SSDs don't do write caching, they do not have enough ram for that. Sandforce for example. > A HW RAID controller is an absolute must for rotating magnetic media, though. > >> Also mdadm is a pain in the ass and is suitable only on amazon and other >> cloud shit. > > I've personally been pretty happy with mdadm. I find the array portability it > offers very useful, so I don't need to buy a second RAID controller just in > case my main controller dies and I need a compatible one to get the array > running again. If you don't need a BBU for safe write-back caching then mdadm > has advantages over hardware RAID. > If we are talking about dedicated machine for database with ssd drives, why would anybody don't by hardware raid for about 500-700$? > I'll certainly use mdadm over onboard fakeraid solutions or low-end hardware > RAID controllers. I suspect a mid- to high end HW RAID unit will generally > win. > > -- > Craig Ringer http://www.2ndQuadrant.com/ > PostgreSQL Development, 24x7 Support, Training & Services
