Re: Do I have a hardware or a software problem?

Craig Ringer <craig@xxxxxxxxxxxxxxx> · Wed, 12 Dec 2012 09:03:14 +0800



    On 12/12/2012 06:44 AM, Evgeny Shishkin
      wrote:

    
        On Dec 12, 2012, at 2:41 AM, Niels Kristian Schjødt <nielskristian@xxxxxxxxxxxxx>
          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. 

    
    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.

    
    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/
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